add workflow (#46)

* Create ci.yml

.github/workflows/ci.yml

@@ -0,0 +1,18 @@
+name: CI
+on: [push, pull_request]
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Test using Node.js
+        uses: actions/setup-node@v1
+        with:
+          node-version: '12'
+      - name: npm install, build, and test
+        run: |
+          npm ci
+          npm run build --if-present
+          npm test
+        env:
+          CI: true