- update references to default branch name in docs, workflows
- use HEAD in github urls, which always works regardless of default branch name
- fix petstore URLs since the old petstore links seem to have stopped working
to merge, in order:
- [x] approve this PR
- [x] rename the default branch to main in settings
- [x] merge this PR
Related tangent: I've been using [this git default-branch](https://github.com/minrk/git-stuff/blob/main/bin/git-default-branch) to help with my aliases and friends working with repos with different branch names.
Signed-off-by: Min RK <benjaminrk@gmail.com>
