Allow action to work on pull_request_target triggers

[patcon]

This should be possible now. Passing in the appropriate token is still required :)

[spkane]

Thank you for submitting this. I need to get this action working with a merge_group as well, so I might use this as a basis to add that support as well.

@belitre @akatov Is there any reason not to get this merged in?

[spkane]

@ouzi-dev Is this something that can be safely merged? I am about to work on a change for merge group support that will likely build on this.