Only execute preview workflow when base ref is main

Signed-off-by: Matheus Cruz <matheuscruz.dev@gmail.com>

Author: mcruzdev

.github/workflows/preview.yml

@@ -16,7 +16,8 @@ jobs:
     if: |
       github.event.workflow_run.event == 'pull_request' &&
       github.event.workflow_run.conclusion == 'success' &&
-      github.event.workflow_run.name == 'Build Website'
+      github.event.workflow_run.name == 'Build Website' &&
+      github.event.workflow_run.head_branch == 'main'
     permissions:
       actions: read
       pull-requests: write