automate workflow for npm publish (#497)

* setup npm_publish workflow and update package.json with new repo info

* refactoring npm publish workflow to reduce dependencies

* npm publish to 2.9.0

* reduce npm publish workflow to publishing task only

* npm publish to 2.9.0

* testing npm publish

* update npm version to 2.9.0 (latest release)

* enhance CONTRIBUTING.md with sentence about npm release workflow

.github/workflows/npm_publish.yml

@@ -0,0 +1,21 @@
+on:
+  release:
+    types: [released]
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          # "ref" specifies the branch to check out.
+          # "github.event.release.target_commitish" is a global variable and specifies the branch the release targeted
+          ref: ${{ github.event.release.target_commitish }}
+      - name: Use Node.js 12
+        uses: actions/setup-node@v1
+        with:
+          node-version: 12
+          registry-url: https://registry.npmjs.org/ # Specifies the registry, this field is required!
+      - run: npm ci
+      - run: npm publish
+        env:
+          NODE_AUTH_TOKEN: ${{ secrets.NPM_AUTOMATION_TOKEN }}