Change default branch to `main`

[trallard]

I suggest we move from master to main - this is pretty straightforward, but we might need to do some link updating in downstream repos

[rgommers]

Makes sense to me. @asmeurer did this for all repos via a script a while back, maybe this one was just missed because the name starts with a period?

[asmeurer]

I added the code of conduct to repos. I didn't do anything with moving master to main. If you change the branch on this repo you'll need to update every code of conduct link in Quansight and Quansight-Labs. You might be able to modify my script (by the way, I never was able to get the script running for Quansight repos because of permissions issues, so you maybe should do that too)

[rgommers]

Argh, confused the two things. That would be a real pain to update - too many repos.