Add a timer

[realroot2185]

Therefore now GRID_ITEM is 4.
Add .gitignore.

Timer value is hardcoded and when it finishes it is restarted.
Not sure to how add submenus and button to change things in TimerState.

[realroot2185]

Oops line 295 in firmware/src/state.rs should have 120 instead of 5
let mut seconds = 5;