Switch default branch to main

[pat-s]

I always get a little "oh no" when switching branches because this project is still using master and doesn't go well with my muscle memory and/or scripts.

@mysticaltech As there is a major release scheduled soon anyhow, I was wondering if it would be within scope to rename the default branch to main?

[mysticaltech]

@pat-s I appreciate the feedback very much. Indeed, main seems to be the new default for most projects. We're going to move to it and that's it. We will do that with V3 that is upcoming ASAP.