Move touche functions into a class

This adds a `Touche` class to the script, which all of the overlapping logic has been moved into. Extracting the functions into a class is a convenient way to group functionality together. I find that this helps the maintainability of the script, because it's possible to start decoupling the class that controls the UI from the other domain logic.

This could go a bit further to make the `checkFont` method leaner, but I didn't want to move a lot of other stuff around at this point.