Add a clippy job to the CI (#163)

* Add clippy CI check

* Fix remaining clippy lints

* Cargo fmt

.github/workflows/check.yml

@@ -29,6 +29,25 @@ jobs:
           command: fmt
           args: --all -- --check
 
+  clippy:
+    runs-on: "ubuntu-latest"
+    steps:
+      - name: Install Rust toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: stable
+          components: clippy
+
+      - uses: actions/checkout@v2
+
+      - name: Cargo clippy
+        uses: actions-rs/cargo@v1
+        with:
+          toolchain: stable
+          command: clippy
+          args: --all-targets --all-features -- -D warnings
+
   test:
     strategy:
       matrix: