Update how-to-access-etcd (#812)

- Break `how-to-access-etcd` into two files:
  - `writing-to-etcd`
  - `reading-from-etcd`
- Rename pages from "How to access ..." to "Writing ..." and "Reading ..."
- Added Prerequisite section
- Removed animated GIF
- Revised procedure to explain keywords

Create reading-from-etcd.md

updating v3.5 with same v3.6 content as above.

Signed-off-by: Nate W <natew@cncf.io>

content/en/docs/v3.5/tutorials/reading-from-etcd.md

@@ -0,0 +1,36 @@
+---
+title: Reading from etcd
+description: Reading a value in an etcd cluster
+weight: 200
+---
+
+## Prerequisites
+
+- Install `etcdctl`
+
+
+## Procedure
+
+Use the `get` subcommand to read from etcd:
+
+```shell
+$ etcdctl --endpoints=$ENDPOINTS get foo
+foo
+Hello World!
+$
+```
+
+where:
+- `foo` is the requested key
+- `Hello World!` is the retrieved value
+
+Or, for formatted output:
+
+```
+$ etcdctl --endpoints=$ENDPOINTS --write-out="json" get foo
+{"header":{"cluster_id":289318470931837780,"member_id":14947050114012957595,"revision":3,"raft_term":4,
+"kvs":[{"key":"Zm9v","create_revision":2,"mod_revision":3,"version":2,"value":"SGVsbG8gV29ybGQh"}]}}
+$
+```
+
+where `write-out="json"` causes the value to be output in JSON format (note that the key is not returned).

content/en/docs/v3.5/tutorials/writing-to-etcd.md

@@ -0,0 +1,20 @@
+---
+title: Writing to etcd
+description: Adding a KV pair to an etcd cluster
+weight: 200
+---
+
+## Prerequisites
+
+- Install `etcdctl`
+
+## Procedure
+
+Use the `put` subcommand to write a key-value pair:
+
+```shell
+etcdctl --endpoints=$ENDPOINTS put foo "Hello World!"
+```
+where:
+- `foo` is the key name
+- `"Hello World!"` is the quote-delimited value

content/en/docs/v3.6/tutorials/reading-from-etcd.md

@@ -0,0 +1,36 @@
+---
+title: Reading from etcd
+description: Reading a value in an etcd cluster
+weight: 200
+---
+
+## Prerequisites
+
+- Install `etcdctl`
+
+
+## Procedure
+
+Use the `get` subcommand to read from etcd:
+
+```shell
+$ etcdctl --endpoints=$ENDPOINTS get foo
+foo
+Hello World!
+$
+```
+
+where:
+- `foo` is the requested key
+- `Hello World!` is the retrieved value
+
+Or, for formatted output:
+
+```
+$ etcdctl --endpoints=$ENDPOINTS --write-out="json" get foo
+{"header":{"cluster_id":289318470931837780,"member_id":14947050114012957595,"revision":3,"raft_term":4,
+"kvs":[{"key":"Zm9v","create_revision":2,"mod_revision":3,"version":2,"value":"SGVsbG8gV29ybGQh"}]}}
+$
+```
+
+where `write-out="json"` causes the value to be output in JSON format (note that the key is not returned).

content/en/docs/v3.6/tutorials/writing-to-etcd.md

@@ -0,0 +1,20 @@
+---
+title: Writing to etcd
+description: Adding a KV pair to an etcd cluster
+weight: 200
+---
+
+## Prerequisites
+
+- Install `etcdctl`
+
+## Procedure
+
+Use the `put` subcommand to write a key-value pair:
+
+```shell
+etcdctl --endpoints=$ENDPOINTS put foo "Hello World!"
+```
+where:
+- `foo` is the key name
+- `"Hello World!"` is the quote-delimited value