Precipitate gitflow into the guide

[sckott]

Seems like we're moving to use gitflow e.g. this link in a number of projects

Is this something we want to make official or only use for certain projects?

Also, seems wise to let users/contribs know in the README/any contrib docs that the project uses this approach so they can follow along accordingly (e.g. avoid PRs to main when almost always should be to dev).

@tefirman @seankross