Changelog:
* Add dark/light mode (toggle via new button beside undo/redo)
* Increase contrast and tweak colors to make everything more visible
* Replace selector/eraser "teardrop" with new "football" model. The teardrop was difficult to see for lots of people
* Hovering over a group now highlights ALL objects in the group, rather than just the hovered object
* Finish a polyline by double-tapping the trigger
* The left-hand palette now disappears less quickly
* Haptic feedback on snap
* Remove intro message