Add publishing automation

.github/workflows/package.yml

@@ -0,0 +1,37 @@
+name: Publish package
+
+on:
+  release:
+    types:
+      - published
+
+jobs:
+  build:
+    name: Build
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+
+      - name: Test
+        uses: actions/setup-node@v1
+        with:
+          node-version: 12
+      - run: npm ci
+      - run: npm run build --if-present
+      - run: npm test
+
+  publish-npm:
+    name: Publish to npm
+    needs: build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-node@v1
+        with:
+          node-version: 12
+          registry-url: 'https://registry.npmjs.org'
+      - run: npm install
+      - run: npm publish
+        env:
+          NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}