Adding branch protection rules to master

[yuhattor]

I got confused with a different PR, merged the unreviewed branch into mainline, and rushed to revert.

The impact was still small now, but is it possible to apply a branch protection rule to master to prevent this from happening in the future?

Related PR: https://github.com/InnerSourceCommons/managing-innersource-projects/pull/22

[rrrutledge]

[yuhattor]

Thank you !