Check custom action usage inside other custom actions by using a queue

[NoelTautges]

This PR fixes bug #58 by using a queue to check custom action usage.

Beginning with the main body of the Shortcut, custom action uses are detected and added to the queue. The function continuously cycles through the queue, adding newly used custom actions, until all possible matches are exhausted.

Notes:

• It makes sure the action isn't already marked as used because otherwise recursive functions go haywire.
• It adds a dummy custom action to make the loop that goes through the queue more clean. This is... questionable, but it does work.
• This PR technically contains 6 commits because of GitHub nonsense, but there's only 2 that actually make changes that haven't already been merged into main.

[NoelTautges]

Hey, guess who accidentally screwed up his pull request by syncing his fork with the upstream repository? It's me, baby! Making a new one in a sec.