Add GitHub actions

Author: Christian Howe

.github/workflows/nodejs.yml

@@ -0,0 +1,21 @@
+name: Node CI
+on: [push]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        node-version: [8.x, 10.x, 12.x]
+    steps:
+    - uses: actions/checkout@v1
+    - name: Use Node.js ${{ matrix.node-version }}
+      uses: actions/setup-node@v1
+      with:
+        node-version: ${{ matrix.node-version }}
+    - run: npm install -g yarn
+    - name: Run tests
+      run: |
+        yarn
+        yarn test
+      env:
+        CI: true