Development flows - discussion and documentation

- Backward / forward compatibility flow (!)
- Create dev wiki/docs that details how the repo is organized and how the project works
- What’s in a major version? 
- Move some of the `discussion` issues into the repository discussions
- Handle versioning in the documentation (documentation for 3.x.x, 4.x.x, 5.x.x, etc...)
- Add section about our tooling (cli, codemod, formatted)
