Enchancement: Put regex in adapt

[David Morris]

I figured out reading the decide-skill repo that regexes need to have their matching group match the filename without extension, and the .rx must be required (not optional) in the intent handler.

By using adapt, we'll be able to make the code shorter and clearer, we'll be closer to the programming style of the wider community, and we'll be able to have multiple phrases for the same action without monstrous regexes, e.g. supporting both "play big buck bunny from my favorites" and "play my starred item big buck bunny."

I'll wait until my previous pull request is resolved to make a pull request on this, since I didn't set up a feature branch for that pull request.