ci: add formatting check

.github/workflows/format.yml

@@ -0,0 +1,22 @@
+name: Check formatting
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+
+permissions: read-all
+
+jobs:
+  prettier:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@a5ac7e51b41094c92402da3b24376905380afc29
+
+      - name: Run prettier
+        uses: creyD/prettier_action@31355f8eef017f8aeba2e0bc09d8502b13dbbad1
+        with:
+          dry: true
+          prettier_options: --check .