Trigger on push to main branch

.github/workflows/publish-image.yml

@@ -9,6 +9,7 @@ on:
   pull_request:
     branches:
       - 'master'
+      - 'main'
 
 # Defines two custom environment variables for the workflow. These are used for the Container registry domain,
 # and a name for the Docker image that this workflow builds.