Add GuardRails GitHub app to Detecting

Add GuardRails GitHub application to the detecting section

README.md

@@ -560,6 +560,7 @@ If you enjoy this awesome list and would like to support it, check out my [Patre
 - [repo-supervisor](https://github.com/auth0/repo-supervisor) - Scan your code for security misconfiguration, search for passwords and secrets.
 - [bXSS](https://github.com/LewisArdern/bXSS) - bXSS is a simple Blind XSS application adapted from [cure53.de/m](https://cure53.de/m) by [@LewisArdern](https://github.com/LewisArdern).
 - [OpenRASP](https://github.com/baidu/openrasp) - An open source RASP solution actively maintained by Baidu Inc. With context-aware detection algorithm the project achieved nearly no false positives. And less than 3% performance reduction is observed under heavy server load.
+- [GuardRails](https://github.com/apps/guardrails) - A GitHub App that provides security feedback in Pull Requests.
 
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 ### Preventing