Add docs for badger (#1431)

* Add docs for badger

This is based on the PR #1424.
Saurabh wasn't able to sign the CLA and that's why I'm raising this PR.

added docs

added gitignore file

updated readme file

updated README.md

* Add missing newlines

* deleted unused file

removed runnable  code files

(cherry picked from commit 2f152d80182adb16913111319591e32714af76ec)

* remove ds_store file

* Added build script and nginx config

Co-authored-by: Apoorv Vardhan <vardhanapoorv@gmail.com>

Author: Ibrahim Jarif

docs/.gitignore

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+/public
+

docs/README.md

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+# Badger Docs
+
+If you are looking for Badger documentation, you might find http://dgraph-badger.geekydev.com/ much more readable.
+
+## Contributing
+
+We use [Hugo](https://gohugo.io/) for our documentation.
+
+### Running locally
+
+ Download and install the latest patch of hugo version v0.69.x from [here](https://github.com/gohugoio/hugo/releases/).
+
+From within the docs folder, run the command below to get the theme.
+
+cd themes && git clone https://github.com/dgraph-io/hugo-docs
+
+Run hugo server within the docs folder and visit http://localhost:1313 to see the documentation site.
+

docs/archetypes/default.md

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+---
+title: "{{ replace .Name "-" " " | title }}"
+date: {{ .Date }}
+draft: true
+---
+

docs/config.toml

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+languageCode = "en-us"
+theme = "hugo-docs"
+canonifyURLs = true
+
+[markup.goldmark.renderer]
+unsafe = true
+
+[markup.highlight]
+noClasses = false
+[[menu.main]]
+  name = "Home"
+  url = "/"
+  identifier = "home"
+  weight = -1
+
+[[menu.main]]
+  name = "Getting Started"
+  url = "/get-started/"
+  identifier = "get-started"
+  weight = 1
+[[menu.main]]
+  name = "Resources"
+  url = "/resources/"
+  identifier = "resources"
+  weight = 2
+
+[[menu.main]]
+  name = "Design"
+  url = "/design/"
+  identifier = "design"
+  weight = 3
+
+[[menu.main]]
+  name = "Project Using Badger"
+  url = "/project-using-badger/"
+  identifier = "project-using-badger"
+  weight = 4
+
+[[menu.main]]
+  name = "Frequently Asked Questions"
+  url = "/faq/"
+  identifier = "faq"
+  weight = 5

docs/content/_index.md

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+---
+title: "BadgerDB Documentation"
+date: 2020-07-06T17:43:29+05:30
+draft: false
+---
+
+![Badger mascot](images/diggy-shadow.png)
+
+BadgerDB is an embeddable, persistent and fast key-value (KV) database written
+in pure Go. It is the underlying database for [Dgraph](https://dgraph.io), a
+fast, distributed graph database. It's meant to be a performant alternative to
+non-Go-based key-value stores like RocksDB.
+
+## Project Status [March 24, 2020]
+
+Badger is stable and is being used to serve data sets worth hundreds of
+terabytes. Badger supports concurrent ACID transactions with serializable
+snapshot isolation (SSI) guarantees. A Jepsen-style bank test runs nightly for
+8h, with `--race` flag and ensures the maintenance of transactional guarantees.
+Badger has also been tested to work with filesystem level anomalies, to ensure
+persistence and consistency. Badger is being used by a number of projects which
+includes Dgraph, Jaeger Tracing, UsenetExpress, and many more.
+
+The list of projects using Badger can be found [here](#projects-using-badger).
+
+Badger v1.0 was released in Nov 2017, and the latest version that is data-compatible
+with v1.0 is v1.6.0.
+
+Badger v2.0 was released in Nov 2019 with a new storage format which won't
+be compatible with all of the v1.x. Badger v2.0 supports compression, encryption and uses a cache to speed up lookup.
+
+The [Changelog] is kept fairly up-to-date.
+
+For more details on our version naming schema please read [Choosing a version](#choosing-a-version).
+
+[Changelog]:https://github.com/dgraph-io/badger/blob/master/CHANGELOG.md

docs/content/contact/_index.md

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++++ 
+title = "Contact" 
+aliases = ["/contact"] 
++++
+
+- Please use [discuss.dgraph.io](https://discuss.dgraph.io) for questions, feature requests and discussions.
+- Please use [Github issue tracker](https://github.com/dgraph-io/badger/issues) for filing bugs or feature requests.
+- Follow us on Twitter [@dgraphlabs](https://twitter.com/dgraphlabs).

docs/content/contact/index.md

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++++ 
+title = "Design" 
+aliases = ["/design"] 
++++
+
+Badger was written with these design goals in mind:
+
+- Write a key-value database in pure Go.
+- Use latest research to build the fastest KV database for data sets spanning terabytes.
+- Optimize for SSDs.
+
+Badger’s design is based on a paper titled _[WiscKey: Separating Keys from
+Values in SSD-conscious Storage][wisckey]_.
+
+[wisckey]: https://www.usenix.org/system/files/conference/fast16/fast16-papers-lu.pdf
+
+## Comparisons
+| Feature                        | Badger                                     | RocksDB                       | BoltDB    |
+| -------                        | ------                                     | -------                       | ------    |
+| Design                         | LSM tree with value log                    | LSM tree only                 | B+ tree   |
+| High Read throughput           | Yes                                        | No                            | Yes       |
+| High Write throughput          | Yes                                        | Yes                           | No        |
+| Designed for SSDs              | Yes (with latest research <sup>1</sup>)    | Not specifically <sup>2</sup> | No        |
+| Embeddable                     | Yes                                        | Yes                           | Yes       |
+| Sorted KV access               | Yes                                        | Yes                           | Yes       |
+| Pure Go (no Cgo)               | Yes                                        | No                            | Yes       |
+| Transactions                   | Yes, ACID, concurrent with SSI<sup>3</sup> | Yes (but non-ACID)            | Yes, ACID |
+| Snapshots                      | Yes                                        | Yes                           | Yes       |
+| TTL support                    | Yes                                        | Yes                           | No        |
+| 3D access (key-value-version)  | Yes<sup>4</sup>                            | No                            | No        |
+
+<sup>1</sup> The [WISCKEY paper][wisckey] (on which Badger is based) saw big
+wins with separating values from keys, significantly reducing the write
+amplification compared to a typical LSM tree.
+
+<sup>2</sup> RocksDB is an SSD optimized version of LevelDB, which was designed specifically for rotating disks.
+As such RocksDB's design isn't aimed at SSDs.
+
+<sup>3</sup> SSI: Serializable Snapshot Isolation. For more details, see the blog post [Concurrent ACID Transactions in Badger](https://blog.dgraph.io/post/badger-txn/)
+
+<sup>4</sup> Badger provides direct access to value versions via its Iterator API.
+Users can also specify how many versions to keep per key via Options.
+
+## Benchmarks
+We have run comprehensive benchmarks against RocksDB, Bolt and LMDB. The
+benchmarking code, and the detailed logs for the benchmarks can be found in the
+[badger-bench] repo. More explanation, including graphs can be found the blog posts (linked
+above).
+
+[badger-bench]: https://github.com/dgraph-io/badger-bench