Change default branch name from master -> main

[cewilliams]

"master" as a branch name has some hostile implications. Suggest we change to "main" for the primary branch. Would need to:

• Rename branch via github repo settings (settings/branches)
• Update github workflow push branch
• Update branch protection in settings if not automatically renamed
• Inform the community members that may have the repo checked out locally

[yuhattor]

Consensus is needed before implementation