Proposal: Migrate master to main

[pd93]

This issue proposes and tracks the changes required to rename Task's master branch to Git's new default branch name: main.
GitHub has a repo that has guidance for changing the default branch from master that informs the rest of this issue.

The steps required to do this are pretty simple:

• Rename master to main
  • Note that (among other things) this will automatically:
    • Re-target any open pull requests
    • Move any branch protection rules that explicitly reference the old name
    • Redirect web requests for the old branch name to the new branch name
  • See docs for instructions and more info.
• Merge chore: update refs from master to main #1048
  • Most of these changes aren't strictly necessary thanks to GitHub's automatic redirection. However, it nice to have everything up to date :)

A note to maintainers of community projects

Very few of the community-made Task projects directly refer to Task's master branch and since GitHub will automatically redirect requests from master to main, there shouldn't be any issues with breaking 3rd party integrations. However, if you do maintain a project that refers to Task's master branch, it's probably a good idea to update any references to main if this issue is completed.

The only project I'm aware of that currently refers to master is the Homebrew formula.

[andreynering]

Opened Homebrew/homebrew-core#128481 to reflect this change on Homebrew.