ci: check formatting

.github/workflows/ci.yml

@@ -0,0 +1,16 @@
+name: CI
+
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+
+jobs:
+  lint:
+    name: Rustfmt
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - name: Run rustfmt
+        run: cargo fmt --all --check