Rename default branch to main?

[ChocolateLoverRaj]

Maybe consider changing the default branch from master to main.

More info:

• https://thenextweb.com/news/github-plans-to-replace-racially-insensitive-terms-like-master-and-whitelist
• https://github.blog/changelog/2020-10-01-the-default-branch-for-newly-created-repositories-is-now-main/

[jackpot51]

Our build system currently uses the master branches as a way to stage releases and we're not in a good spot to transition. There is a PR for that here: pop-os/pop#2075