Add GitHub Actions

.github/workflows/integrate.yml

@@ -0,0 +1,19 @@
+name: Continuous Integration
+
+on:
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  test_pull_request:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-node@v1
+        with:
+          node-version: 12
+      - run: npm ci
+      - run: cd functions && npm ci
+      - run: npm run test
+      - run: cd ..
+      - run: npm run build