ci: add rust fmt check for pull requests

.github/workflows/rust-fmt.yml

@@ -0,0 +1,18 @@
+on: pull_request
+
+name: Rustfmt
+
+jobs:
+  format:
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@nightly
+        with:
+          components: rustfmt
+      - uses: mbrobbel/rustfmt-check@master
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          mode: review