added concurrency limit to stop double runs

this way if a new commit is pushed the old action will be stopped. It will only happen in PRs and not in the master branch

.github/workflows/docs.yml

@@ -8,6 +8,10 @@ on:
     types: [opened, synchronize, reopened, ready_for_review, labeled]
   merge_group:
 
+concurrency:
+  group: ${{ github.ref }}
+  cancel-in-progress: ${{ github.ref != 'refs/heads/master' }}
+
 jobs:
   set-image:
     # GitHub Actions allows using 'env' in a container context.