[ci] Add file mode test to code check (#13036)

Authored by: Grub4K

.github/workflows/quick-test.yml

@@ -38,3 +38,5 @@ jobs:
       run: ruff check --output-format github .
     - name: Run autopep8
       run: autopep8 --diff .
+    - name: Check file mode
+      run: git ls-files --format="%(objectmode) %(path)" yt_dlp/ | ( ! grep -v "^100644" )