Add support for active-high menu buttons

Summary

Hey folks, first of all, thanks for such an amazing library!

I already completed and ordered a hardware part for my project, when I realized the library can only handle active-low button events (while the project is already set up for active-high).

It will be a great addition if the library could support active-high as well. Currently, I simply patch the following function to achieve the desired result:

// changed from
u8x8_SetGPIOResult(u8x8, digitalRead(i) == 0 ? 0 : 1);
// changed to
u8x8_SetGPIOResult(u8x8, digitalRead(i) == 1 ? 0 : 1);

but this approach is not reliable as the library could change at any time.

Instead, there could be a simple flag, let's say U8X8_USE_ACTIVE_HIGH:

#ifdef U8X8_USE_ACTIVE_HIGH
  u8x8_SetGPIOResult(u8x8, digitalRead(i) == 1 ? 0 : 1);
#else
  u8x8_SetGPIOResult(u8x8, digitalRead(i) == 0 ? 0 : 1);
#endif // U8X8_USE_ACTIVE_HIGH

I may try raising a PR with proposed solution from above once I have a bit of time 🙌

olikraus / u8g2

Add support for active-high menu buttons #2214

Summary