ci: Check code formatting with cargo fmt

Author: ravenexp

.github/workflows/rust.yml

@@ -21,3 +21,10 @@ jobs:
       run: cargo build --verbose
     - name: Run tests
       run: cargo test --verbose
+  fmt:
+    name: Check code formatting
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - name: Run cargo fmt
+      run: cargo fmt -- --check