Add CI action

.github/workflows/ci.yml

@@ -0,0 +1,20 @@
+on: [push]
+
+jobs:
+  test:
+    name: Test on Node.js ${{ matrix.node_version }}
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        node_version: [8, 10]
+
+    steps:
+    - uses: actions/checkout@master
+    - name: Use Node.js ${{ matrix.node_version }}
+      uses: actions/setup-node@v1
+      with:
+        version: ${{ matrix.node_version }}
+    - name: npm install, build, and test
+      run: |
+        npm install
+        npm test