Add release trigger.

Author: lpeabody

Diff for: .github/workflows/build-push.yml

@@ -2,8 +2,9 @@ name: Build and push
 
 on:
   push:
-    branches:
-      - main
+    branches: [main]
+  release:
+    types: [published]
 
 env:
   REGISTRY: ghcr.io