Migrate this repository's default branch from master to main?

[yuvipanda]

This has been done for most repositories in the jupyter / jupyterhub ecosystem, but I think not been done for this repository. We should do the migration as well.

I haven't done this before though, so am not sure what exactly it entails. I do think it's not too bad though?

EDIT: How to go about this is documented in jupyterhub/team-compass#412

[consideRatio]

I think doing it is fine and reasonable, concrete steps to do it can be found in jh team-compass issue by Simon - these migrations have been quick and simple i'd say

[jmunroe]

This makes sense to me! I've been noticing that I have to consciously remember that this repo is still using master and it routinely trips me up.