Add GH action for clippy checks (#208)

Add GH action for clippy checks

.github/workflows/clippy.yml

@@ -0,0 +1,18 @@
+on: [push, pull_request]
+
+name: Clippy check
+jobs:
+  clippy_check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - run: rustup component add clippy
+      - uses: actions-rs/toolchain@v1
+        with:
+          toolchain: stable
+          target: thumbv7m-none-eabi
+          override: true
+      - uses: actions-rs/clippy-check@v1
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          args: --features=stm32f103 --target thumbv7m-none-eabi