fix: only run publish workflow once per tag

Author: mugikhan

.github/workflows/publish.yml

@@ -7,6 +7,10 @@ on:
       - "powersync_flutter_libs-v[0-9]+.[0-9]+.[0-9]+*"
   workflow_dispatch:
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: false
+
 jobs:
   publish-packages:
     name: Publish packages