Initial Button Support

Gossan has initial support for buttons! While this version of the runtime doesn't yet cover all of Pebble's API surface for clicks, supporting window_set_click_config_provider, window_single_click_subscribe, and a handful of related functions are enough to play Tiny Bird and Mr.Runner on your Playdate!

I mapped Playdate's d-pad to Pebble's four buttons and so far, this is working fine. I am considering mapping Playdate's b-button to one of Pebble's buttons for titles that really only use one button (I have one particular game in mind, of course…). The UI inspects the running watch application so that only clicks that will have an effect on the app will be indicated as such. As part of this work, I also rewrote the screen update routines to take advantage of Playdate's sprite system.

This enables some fancy developer tooling in the Playdate simulator when highlighting screen updates (see tinted overlays in the GIF above). My hope is that this will also fix a funny bug reported by merryt that may occur in conjunction with Playdate's low power warning  🤞

Known Limitations: Highscores are currently not persisted. So if you ever make it past the first obstacle in Tiny Bird, make sure to take a picture!