lint-hotkeys: Add linting for HELP_CATEGORIES.

- Implemented a linting check to ensure all `key_category` values in
  `KEY_BINDINGS` are present in the `HELP_CATEGORIES` dictionary.
- Added functionality to print any missing categories if they are not
  found in `HELP_CATEGORIES`.

Author: rsashank

Diff for: tools/lint-hotkeys

@@ -30,6 +30,7 @@ def main(fix: bool) -> None:
     if fix:
         generate_hotkeys_file()
     else:
+        lint_help_categories()
         lint_hotkeys_file()
 
 
@@ -80,6 +81,21 @@ def lint_hotkeys_file() -> None:
     sys.exit(error_flag)
 
 
+def lint_help_categories() -> None:
+    """
+    Check if HELP_CATEGORIES contains all key categories
+    """
+    missing_categories = [
+        binding['key_category'] for binding in KEY_BINDINGS.values()
+        if binding['key_category'] not in HELP_CATEGORIES
+    ]
+    if missing_categories:
+        print(
+            f"Missing categories in HELP_CATEGORIES (keys.py file): {missing_categories}"
+        )
+        sys.exit(1)
+
+
 def generate_hotkeys_file() -> None:
     """
     Generate OUTPUT_FILE based on help text description and