Add Cargo CI action

Runs `cargo check` and `cargo clippy` on the latest nightly.

.github/workflows/rust.yml

@@ -0,0 +1,32 @@
+name: Rust
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  check:
+    name: cargo check and Clippy
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install latest nightly
+        uses: actions-rs/toolchain@v1
+        with:
+            toolchain: nightly
+            override: true
+            components: rustfmt, clippy
+
+      # `cargo check` command here will use installed `nightly`
+      # as it is set as an "override" for current directory
+
+      - name: Run cargo check
+        uses: actions-rs/cargo@v1
+        with:
+          command: check
+      - name: Run Clippy
+        uses: actions-rs/cargo@v1
+        with:
+          command: clippy