Add npm publish automation (#117)

* build: creating release triggers NPM publish github action

.github/workflows/npm-publish.yml

@@ -0,0 +1,18 @@
+name: NPM publish
+on:
+  release:
+    types: [published]
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - uses: actions/setup-node@v1
+        with:
+          node-version: 14
+      - run: npm install
+      - run: npm test
+      - uses: JS-DevTools/npm-publish@v1
+        with:
+          token: ${{ secrets.NPM_TOKEN }}