feat: add pre-start trigger for notifying on application start

Closes #2713

plugins/ps/functions

@@ -93,6 +93,7 @@ ps_start() {
   local IMAGE_TAG=$(get_running_image_tag "$APP");
 
   if (is_deployed "$APP"); then
+    plugn trigger pre-start "$APP"
     if ! (is_app_running "$APP"); then
       release_and_deploy "$APP" "$IMAGE_TAG"
     else