Fix workflow permissions for repository dispatch

- Change contents permission from read to write
- Required for GITHUB_TOKEN to create repository dispatch events
- Enables automatic demo updates after latest tag builds

Author: codebude

.github/workflows/docker-build.yml

@@ -14,7 +14,7 @@ on:
         type: boolean
 
 permissions:
-  contents: read
+  contents: write
   packages: write
 
 jobs: