This PR adds internal docs directly to the codebase.

There are a few goals here:

- Make it easier to document our internal processes
- Put the documentation where people already are
- Allow changes to be in sync with PRs
- Make it easier for people coming in to discover our docs and onboard
faster.

With 2 more people joining us in the next few weeks it would be great to
get these up.

Release Notes:

- N/A (No public facing changes)