Get ready moving master into main

[Natim]

Refs #692

Local procedure for contributors

git branch -m master main
git fetch origin
git branch -u origin/main main
git remote set-head origin -a

[leplatrem]

Yes, why not :)
Let's release first and do this!
We have a few repos to align with that then ;)

[leplatrem]

After thinking about this, I'd prefer to either do all repos in the Kinto org, or none of them

[leplatrem]

Realized some references to master still exist in the GH actions configs

[Natim]

I'd prefer to either do all repos in the Kinto org, or none of them

In anycase you will not be able to merge all of them at once. Feel free to merge it whenever you want.