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/src/activity.c

@@ -74,8 +74,8 @@ void activity_work_handler(struct k_work *work) {
     } else
 #endif /* IS_ENABLED(CONFIG_ZMK_SLEEP) */
         if (inactive_time > MAX_IDLE_MS) {
-        set_state(ZMK_ACTIVITY_IDLE);
-    }
+            set_state(ZMK_ACTIVITY_IDLE);
+        }
 }
 
 K_WORK_DEFINE(activity_work, activity_work_handler);