feat: add rollback_on_failure feature (#88)

This PR adds the ability to download existing code before deployment and automatically roll back if the post-deployment monitor detects a failure.

Reviewed-on: #88
Reviewed-by: LLMReview <27+autoreview@noreplay.horstenkamp.eu>

action.yaml

@@ -67,6 +67,10 @@ inputs:
     description: 'Print a progress update every N ticks when log_to_file=true (default: 10).'
     required: false
     default: '10'
+  rollback_on_failure:
+    description: 'Automatically rollback to previous code if the monitor detects failures. Requires monitor > 0. (default: false)'
+    required: false
+    default: 'false'
 outputs:
   saw_traceback:
     description: true if a JS traceback was detected during monitoring.