WIP: Document packaging repositories

[legoktm]

Status

Work in progress

Description of Changes

Document how all the packaging repositories, how they work, etc.

Fixes #80.

• Related Issues

Testing

*

Release

Checklist (Optional)

• [ ] Doc linting (make docs-lint) passed locally
• [ ] Doc link linting (make docs-linkcheck) passed
• [ ] You have previewed (make docs) docs at http://localhost:8000

[legoktm]

This is a very rough WIP, needs more expansion, formatting, etc.