Add GitHub Actions

.github/workflows/ci.yml

@@ -0,0 +1,21 @@
+on: [push, pull_request]
+
+name: CI
+
+jobs:
+  test:
+    name: cargo test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions-rs/toolchain@v1
+        with:
+          toolchain: stable
+          profile: minimal
+          default: true
+      - uses: actions-rs/cargo@v1
+        with:
+          command: build
+      - uses: actions-rs/cargo@v1
+        with:
+          command: test