ci: allow to manually run gh-pages build

Author: mdeanjones

.github/workflows/gh-pages.yml

@@ -4,7 +4,7 @@ on:
   push:
     branches: [ 'main' ]
     paths: [ './addon', './storybook', './storybook-utilities' ]
-  workflow_call:
+  workflow_dispatch:
 
 jobs:
   deploy: