Add to Migration, Syntax, and Contribution Guides

[bmorelli25]

Summary

• Adds to migration, syntax, and contribution guides
• Adds issue templates for bugs and enhancements
• Adds scripts helpful for migration tasks

[bmorelli25]

@elastic/docs-engineering I wonder if there's somewhere better to put these scripts instead of in the docs dir? A consideration is that some of these scripts output .md files that are included in the docs.

[Mpdreamz]

@bmorelli25 can you describe a bit what the intended use case is for these ?

Who runs them and when? is this a continuous thing?

[bmorelli25]

Good question. They're documented in the source files in this PR. But a brief summary is:

1. CODEOWNER list for documentation freeze
   This script creates a list of repositories and the directories in those repositories that the @docs-freeze-team (just @KOTungseth) should be added as codeowner of. During a documentation freeze, the @docs-freeze-team must approve any pull requests that modify .asciidoc files before they can be merged. This prevents folks from merging docs changes during the freeze.

2. Attribute converter
   This script converts the attributes in https://github.com/elastic/docs/blob/master/shared/attributes.asciidoc to the supported yaml format for docs-builder.

1. HTML to Markdown Tab Converter
The tab converter script is used to convert HTML tabs into Markdown tabs within documentation files. The script scans through specified directories, finds all Markdown (.md) files, and replaces any HTML-based tab structures with their Markdown equivalents.
This is no longer necessary as @siamakp-elastic added this capability to the migration tool. I've removed this script from this PR.

[Mpdreamz]

1. Is this something that needs to run continuously in the future or is this a one of thing?

2. Same question really, but also:

   • Do we need all of these in the new architecture?
   • Rather then having these live in all of the isolated docset.yml files should docs-builder natively support them?

[bmorelli25]

Is this something that needs to run continuously in the future or is this a one of thing?

Okay so after a meeting today, the CODEOWNER script won't be used so we can get rid of it. We will need to rerun the attribute converter eventually (Jan 29) but I can do that so there's no need to put it here (won't be used after that date). I'll remove both from this PR.

Do we need all of these in the new architecture?

All, no. Most, yes.

Rather then having these live in all of the isolated docset.yml files should docs-builder natively support them?

Yes. The more I play with this, the more a single yml file where these can be defined would be ideal.

[bmorelli25]

The build is currently failing with

Error: Not linked in toc: migration/scripts/codeowner-gen/output.md

Opened a bug for this: #169

[bmorelli25]

As discussed above, I removed the scripts from this PR. That also fixed the build error. I'm going to get this merged so that the GH pages is updated.