Avoid releasing version on certain commits

[fregante]

Some commits don't need to be released as their own version, so there could be a way to ignore them. For example this can be done via ignore an option that excludes commits based on their title (like this other action) or simply by detecting [norelease] in the commit description

Current logic:

if HEAD is tagged
	exit

Desired logic:

commit = HEAD
while commit is ignored
	commit = commit.parent

if commit is tagged
	exit