Changed the label property on zmk,ext-power-generic to be optional and
removed it from existing uses. Renamed the nodes for all non-development
boards to "EXT_POWER" to preserve user settings.
rgb_underglow.c now finds the correct device by finding the first
instance of zmk,ext-power-generic instead of looking for a node named
"EXT_POWER".
Updated existing pre-commit hooks and added some new hooks:
- Remove trailing whitespace
- Ensure every non-empty file ends with a new line
- Check YAML file validity
- Prevent adding large files
- Ensure any scripts with shebangs are executable
Added a GitHub action to run pre-commit on every commit. Removed any
existing actions which duplicate pre-commit.
Ran pre-commit on the codebase.
