refactor: Add more checks to pre-commit

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.

app/boards/shields/splitreus62/Kconfig.defconfig

@@ -1,8 +1,8 @@
 
 # Copyright (c) 2020 Derek Schmell
 # SPDX-License-Identifier: MIT
- 
- 
+
+
 if SHIELD_SPLITREUS62_LEFT
 
 config ZMK_KEYBOARD_NAME
@@ -17,5 +17,5 @@ if SHIELD_SPLITREUS62_LEFT || SHIELD_SPLITREUS62_RIGHT
 
 config ZMK_SPLIT
 	default y
-	
+
 endif