…king this from the navigation menu

Re-group how-to's
Add an introductory sentence per category
Re-order list items
Add a linkcheck_ignore item for www.breezy-vcs.org which is not reachable.

Update the "Project and community" section to have links to contribute to both code and docs
Make the call to action to log issues on GitHub stronger, and emphasise discussion via other channels
Position the general tips as a helpful way to ensure better quality documentation
Re-arrange some content to flow a bit better