add github workflow

.github/workflows/main.yaml

@@ -0,0 +1,27 @@
+name: main
+
+on:
+  push:
+    branches: [ cli ]
+  pull_request:
+    branches: [ cli ]
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  format:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: checkoout
+      uses: actions/checkout@v3
+
+    - name: Install latest rust
+      uses: dtolnay/rust-toolchain@master
+      with:
+          toolchain: stable
+          components: rustfmt
+
+    - name: Format
+      run: cargo fmt -- --check