add CI representation
the representation of a CI is normalized to be a directory that has the same structure as .forgejo/workflows
and the same feature set. Converting from Woodpecker CI to the F3 format is a matter of trying to map transform the yaml in the same way the drone to woodpecker conversion utility was done.
This documentation can be the reference that will be used by Forgejo to document Forgejo Action so that it is 100% compliant from the start.