feature request: detect default branch or GitHub Pages branch

[LayZeeDK]

There are a few common branch names:

• gh-pages
• main
• master

Instead of using master as the default branch name, why don't we detect what the default branch is in the GitHub repo this action is running in?

• Using the GitHub CLI which is preinstalled in GitHub runners
• Using the GitHub REST API

There might even be an API for detecting the exact branch used for GitHub Pages in the GitHub repo the action is running in.