feature: request: Buttons not detected

[studioj]

hey, just bumped into your lib it looks pretty nice (the waveshare default lib isnt super user-friendly :-s)

i noticed you don't check for button gpios I think most of the displays come with 4 side buttons.
Would you be ok with me opening a PR to add this functionality... ?
(thinking abt multiple ways => really like how gpiozero works but maybe you think that library is to large to add to dependencies
=> if so it'll take a bit longer to get it working in a similar matter, and of course the extra maintenance :-s )