Add a git section to the FAQ

[AureliaDolo]

Especially with the transition from gitlab to github

What do you think @Noxhaa

[Noxhaa]

Could be useful, but I don't get specific questions about it, so it's gonna be a bit general on how git works

[AureliaDolo]

Maybe when someone has an issue with git you can get into the habit of writing the answer in the doc. I've seen someone with a fatal: destination path 'massa' already exists and is not an empty directory. git error, maybe it was the only one x)

[Noxhaa]

I'll lookout and note massa specific git issues :)

[AureliaDolo]

I move that to discussion. Feel free to edit the wiki when you encounter recurring issues :)