Add GitHub actioni to run tests on PR (#180)

.github/workflows/build.yaml

@@ -0,0 +1,24 @@
+name: Node.js CI
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - name: Use Node.js
+        uses: actions/setup-node@v1
+        with:
+          node-version: '12.x'
+      - name: Install dependencies
+        run: npm install
+      - name: Build
+        run: npm test
+        env:
+          CI: true