Add support for watching additional files in watch mode

[michaelhthomas]

In a project I am currently working on, I have a typst paper within a larger python project, and am importing code from python modules in the same directory. It would be great to be able to pass a wildcard, i.e. *.py to the watch command, and have it reset the cache and rebuild when any of the matched files changes. This could also be useful for input data files, i.e. a wildcard on *.csv or the like.

[patrick-kidger]

Sounds reasonable to me. Happy to take a PR on this :)