ci(helm): publish chart on tag push

Trigger the helm release workflow automatically on tag pushes so each
software release also publishes the chart to gh-pages and the OCI
registry at ghcr.io/seaweedfs. workflow_dispatch is kept as a manual
fallback.

Refs #6296

.github/workflows/helm_manual_release.yml

@@ -1,6 +1,9 @@
-name: "helm: manual release"
+name: "helm: release"
 
 on:
+  push:
+    tags:
+      - '*'
   workflow_dispatch:
 
 permissions: