ci: new stylua action that only runs on push

.github/PULL_REQUEST_TEMPLATE.md

@@ -2,4 +2,3 @@
 - [ ] Used only camelCase variable names.
 - [ ] If functionality is added or modified, also made respective changes to the
   `README.md` (the `.txt` file is auto-generated and does not need to be modified).
-- [ ] If a non-trivial PR, formatting via `stylua`.

.github/workflows/stylua.yml

@@ -0,0 +1,20 @@
+name: Format with Stylua
+
+on:
+  push:
+    branches: [ main ]
+    paths: [ '**.lua' ]
+
+jobs:
+  postprocessing:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: JohnnyMorganz/stylua-action@v4
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          version: latest
+          args: --check .
+      - uses: stefanzweifel/git-auto-commit-action@v4
+        with:
+          commit_message: "style: format with stylua"