👷 add concurrency control to docker.yml workflow to prevent overlapping runs

Author: techouse

.github/workflows/docker.yml

@@ -6,6 +6,10 @@ defaults:
   run:
     shell: bash
 
+concurrency:
+  group: docker-${{ github.ref }}
+  cancel-in-progress: false
+
 jobs:
   push_to_registry:
     name: Push Docker image to Docker Hub