ci: add Rustfmt check workflow (#22)

- Add GitHub Actions workflow for Rust formatting check
- Workflow runs on push and pull request events
- Uses stable Rust toolchain with rustfmt component
- Checks code formatting using cargo fmt

Signed-off-by: jinlong <jinlong@tencent.com>

Author: fslongjin

.github/workflows/format.yml

@@ -0,0 +1,21 @@
+name: Format Check
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  rustfmt:
+    name: Rustfmt Check
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Install Rust toolchain
+        uses: dtolnay/rust-toolchain@stable
+        with:
+          components: rustfmt
+
+      - name: Check formatting
+        run: cargo fmt --all -- --check