ci: add npm release workflow

Author: Enda Phelan

Diff for: .github/workflows/main.yml

@@ -7,6 +7,8 @@ on:
   pull_request:
     branches:
       - master
+  release:
+      types: [released, prereleased]
 
 jobs:
   test:
@@ -54,3 +56,22 @@ jobs:
           else    
               echo "Skipping canary publish due to a fork/PR..."
           fi
+
+  publish:
+    # publish to npm only when doing the release
+    if: ${{ github.event_name == 'release' }}
+    name: Publish Release
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout Master
+        uses: actions/checkout@v1
+      - name: Use Node
+        uses: actions/setup-node@v1
+        with:
+          node-version: 14
+      - name: Install Dependencies using Yarn
+        run: yarn install
+      - name: Build
+        run: yarn build
+      - name: Release
+        run: echo "//registry.npmjs.org/:_authToken=${{secrets.NODE_AUTH_TOKEN}}" > ~/.npmrc && TAG=${GITHUB_REF#"refs/tags/"} npm run release