👷 build and deploy on releases only

Author: Joseph Hirsch

.github/workflows/build-demonstrator.yaml

@@ -1,10 +1,8 @@
 name: Create and publish a Docker image
 
 on:
-  push:
-    branches: [ main ]
-  pull_request:
-    branches: [ main ]
+  release:
+    types: [published]
 
 env:
   REGISTRY: ghcr.io