feat: add branch param

[WingLim]

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See the Disscusions: Homebrew/discussions#1492

Add a --branch param for pr-publish.
So that we could trigger github action with pr-publish in a tap(Third Party Repository) without using master as default branch.

And for keeping homebrew-core work normally, the default is set to master, so no need to change the github actions in homebrew-core.

[MikeMcQuaid]

Thanks so much for your first contribution! Without people like you submitting PRs we couldn't run this project. You rock, @WingLim!