Add to list of resources for learning git

[Bradamant3]

Not sure we've even got a list to add to yet, except in the newsletter. But we should. In the meantime, parking a twitter thread with some resources i don't think we have written up elsewhere:
https://twitter.com/ceeoreo_/status/1336099829659930631

[plaindocs]

Only this :-( https://www.writethedocs.org/guide/learn-git-contribute/

Which does surprise me.

But adding Git to https://www.writethedocs.org/guide/#tools-of-the-trade and the folding the above in with other resources makes sense.

[BazenGabrakirstos]

This one is really user friendly https://product.hubspot.com/blog/git-and-github-tutorial-for-beginners