Set up GitHub workflow

.github/workflows/ci.yml

@@ -0,0 +1,22 @@
+name: ci
+
+on: [ push, pull_request ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Node.js v12
+      uses: actions/setup-node@v1
+      with:
+        node-version: 12
+
+    - name: Set up node modules
+      run: npm ci
+
+    - name: Execute tests
+      run: npm run test
+
+    - name: Build artifacts
+      run: npm run build