chore(docker-hub): add github action for docker hub readme update

Author: solidnerd

.github/workflows/main.yml

@@ -33,3 +33,9 @@ jobs:
         repository: solidnerd/bookstack
         tag_with_ref: true
         add_git_labels: true
+    - name: Docker Hub Description
+      uses: peter-evans/dockerhub-description@v2
+      env:
+        DOCKERHUB_USERNAME: ${{ secrets.DOCKER_USERNAME }}
+        DOCKERHUB_PASSWORD: ${{ secrets.DOCKER_PASSWORD }}
+        DOCKERHUB_REPOSITORY: solidnerd/bookstack