feat: Implement barebones Forum channel support.

[FayeDel]

About

This PR title essentially explains itself. Forums are in testing but has been more widespread, so this is left as a draft PR until its live/more features are discovered.

This correlates to an earlier PR: #630

Checklist

• [X] I've ran pre-commit to format and lint the change(s) made.
• [X] I've checked to make sure the change(s) work on 3.8.6 and higher.
• [ ] This fixes/solves an Issue.
  • (If existent):
• [X] I've made this pull request for/as: (check all that apply)
  • [X] Documentation
  • [X] Breaking change
  • [X] New feature/enhancement
  • [ ] Bugfix

[i0bs]

As of 5 July.

[FayeDel]

Forums are officially out so I'm marking this as ready for review ^^

[EepyElvyra]

Docs build failed