Update pantheon-deploy-to-staging.yml

Author: vfalconisumo

.github/workflows/pantheon-deploy-to-staging.yml

@@ -1,11 +1,12 @@
-name: deploy-to-pantheon-prod
+name: deploy-to-pantheon-staging
 
 permissions:
   deployments: write
   contents: write
   pull-requests: read
 
 on:
+  workflow_dispatch:
   push:
     branches:
       - staging/**