- Offer more hand-holding at the start.
- Clean up dev environment setup steps.
- Move joining CZO later in the process.
- Move feedback section to feature suggestions page.
- Drop other non-coding info, as it exists elsewhere.
- Updates instances of "private message", "PM", and "private_message",
excluding historical references in `overview/changelog.md`.
- Also excludes `/docs/translating` since we would need new
translations for "direct messages" and "DMs".