GHA: sync README.md to Docker Hub

.github/workflows/sync-readme.yml

@@ -0,0 +1,23 @@
+name: Sync README.md to Docker Hub
+
+on:
+  push:
+    branches:
+      - master
+
+jobs:
+  sync:
+    name: Sync README
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout HEAD
+        uses: actions/checkout@v1
+
+      - name: Sync README
+        uses: ms-jpq/sync-dockerhub-readme@e2991ea1ba48832e73555cdbd5b82f5a2e91ee9b # v1
+        with:
+          username: icingaadmin
+          password: '${{ secrets.DOCKER_HUB_PERSONAL_TOKEN }}'
+          repository: icinga/icingaweb2
+          readme: ./README.md