Add CI.

.github/workflows/ci.yml

@@ -0,0 +1,40 @@
+name: Rust CI
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  build:
+    name: Test and Benchmark
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        rust-version: [stable, nightly]
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v2
+
+    - name: Set up Rust - Stable
+      if: matrix.rust-version == 'stable'
+      uses: actions-rs/toolchain@v1
+      with:
+        toolchain: stable
+        profile: minimal
+
+    - name: Set up Rust - Nightly
+      if: matrix.rust-version == 'nightly'
+      uses: actions-rs/toolchain@v1
+      with:
+        toolchain: nightly
+        profile: minimal
+
+    - name: Test
+      if: matrix.rust-version == 'stable'
+      run: cargo test
+
+    - name: Bench
+      if: matrix.rust-version == 'nightly'
+      run: cargo bench