Add github action to auto-update docker repo version on release publish

.github/workflows/build.yml

@@ -0,0 +1,37 @@
+name: PublishDockerImage
+
+on:
+  release:
+    types: [published]
+
+jobs:
+  generate:
+    name: 'Update node-red-docker image'
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out node-red repository
+        uses: actions/checkout@v2
+        with:
+            path: 'node-red'
+      - name: Check out node-red-docker repository
+        uses: actions/checkout@v2
+        with:
+            repository: 'node-red/node-red-docker'
+            path: 'node-red-docker'
+      - uses: actions/setup-node@v1
+        with:
+            node-version: '12'
+      - run: node ./node-red/.github/scripts/update-node-red-docker.js
+        id: updateFiles
+      - name: Create Pull Request
+        uses: peter-evans/create-pull-request@v2
+        with:
+          token: ${{ secrets.NR_REPO_TOKEN }}
+          committer: GitHub <noreply@github.com>
+          author: ${{ github.actor }} <${{ github.actor }}@users.noreply.github.com>
+          path: 'node-red-docker'
+          title: '[TEST] Update to Node-RED ${{ env.newVersion }} release'
+          body: |
+            Updates the Node-RED Docker repo for the ${{ env.newVersion }} release.
+
+            This PR was auto-generated by a GitHub Action. Any questions, speak to @knolleary