github: add Clippy check to CI

.github/workflows/build.yml

@@ -27,3 +27,19 @@ jobs:
     - name: Test
       run: |
         cargo test --workspace --verbose
+
+  clippy:
+    name: Clippy check
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions-rs/toolchain@v1
+        with:
+          toolchain: nightly
+          components: clippy
+          override: true
+      - run: rustup component add clippy
+      - uses: actions-rs/clippy-check@v1
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          args: --all-features --workspace