ci: add clippy workflow task.

This ensures `cargo clippy` is run consistently, and denies warnings.

Author: cpu

.github/workflows/ci.yml

@@ -11,6 +11,20 @@ env:
   RUSTFLAGS: -D warnings
 
 jobs:
+  clippy:
+    name: Clippy
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout sources
+        uses: actions/checkout@v3
+        with:
+          persist-credentials: false
+      - name: Install rust toolchain
+        uses: dtolnay/rust-toolchain@stable
+        with:
+          components: clippy
+      - run: cargo clippy --all --all-features -- --deny warnings
+
   build-windows:
     runs-on: windows-latest
     steps: