Add GH publish action (#13)

* Add GH publish action

Adds an automatic npm module publish GH Action on tag.

.github/workflows/publish.yml

@@ -0,0 +1,22 @@
+on:
+  push:
+    tags:
+      - 'v[0-9]+.[0-9]+.[0-9]+*'
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: read node.js version
+        id: nodejs-version
+        run: |
+          content=`cat ./.nvmrc`
+          echo "::set-output name=content::$content"
+      - uses: actions/setup-node@v2
+        with:
+          # See https://github.com/actions/setup-node/issues/32
+          node-version: ${{ steps.nodejs-version.outputs.content }}
+      - run: npm install
+      - uses: JS-DevTools/npm-publish@v1
+        with:
+          token: ${{ secrets.NPM_TOKEN }}

.nvmrc

@@ -0,0 +1 @@
+14.15.1