Allow other branch names than master in GitHub action

[stigok]

GitHub is switching the default branch name from master to main. Currently refs/heads/master is hard-coded. It would be good to have this configurable.

palisade/src/cmd/github_action.rs

Lines 8 to 11 in 4eef8be

	if gha.refname != "refs/heads/master" {
	println!("doesn't need to run on non-master branches");
	return Ok(());
	}