This commit adds a new keycode `RGB_SMOD` which is the same as `RGB_MOD` (cycle through all modes),
but when it is used in combination with shift it will reverse the direction.
- a keyboard already in bootloader mode will now be detected
- if setting the keyboard to bootloader mode doesn't work, a hint will be printed on how to do so
- instead of failing instantly when no keyboard is found, the script will now wait up to 60 seconds (it retries every 5 seconds, up to 12 times)
Sebastian Kaim