[Fix] Publish docker image only on push to main.

Add an action that runs a build (with tests) on PR/push to main.

.github/workflows/merge-to-protected.yml

@@ -0,0 +1,37 @@
+# This is a basic workflow to help you get started with Actions
+
+name: CI
+
+# Controls when the action will run. Triggers the workflow on push or pull request
+# events but only for the master branch
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+# A workflow run is made up of one or more jobs that can run sequentially or in parallel
+jobs:
+  # This workflow contains a single job called "build"
+  build:
+    # The type of runner that the job will run on
+    runs-on: ubuntu-latest
+
+    # Steps represent a sequence of tasks that will be executed as part of the job
+    steps:
+      # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
+      - uses: actions/checkout@v2
+      - name: Use Node.js
+        uses: actions/setup-node@v1
+        with:
+          node-version: "16.x"
+      - name: Install
+        run: npm install
+      - name: Build
+        run: npm run-script build
+        env:
+          CI: ""
+      - name: Test
+        env:
+          NODE_OPTIONS: "--max-old-space-size=4096"
+        run: npm run-script test

.github/workflows/publish-docker-image.yml

@@ -3,8 +3,6 @@ name: Publish Docker Image
 on:
   push:
     branches: [ main ]
-  pull_request:
-    branches: [ main ]
   workflow_dispatch:
 env:
   # Last fragment of identifier of the docker image