ci: add CI for clippy, rustfmt and shell scripts (#193)

.github/workflows/clippy.yml

@@ -0,0 +1,30 @@
+name: Clippy check
+
+on:
+  push:
+    branches:
+      - 'main'
+    paths:
+      - '.github/workflows/clippy.yml'
+      - 'userspace/ksud/**'
+
+env:
+  RUSTFLAGS: '-Dwarnings'
+
+jobs:
+  clippy:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - uses: Swatinem/rust-cache@v2
+        with:
+          workspaces: userspace/ksud
+
+      - name: Install cross
+        run: cargo install cross
+
+      - name: Run clippy
+        run: |
+          cross clippy --manifest-path userspace/ksud/Cargo.toml --target aarch64-linux-android
+          cross clippy --manifest-path userspace/ksud/Cargo.toml --target x86_64-linux-android