extend readme with webhook related note

README.md

@@ -6,3 +6,12 @@ This contains key golang libraries for Forta services.
 ## Bug Bounty
 
 We have a [bug bounty program on Immunefi](https://immunefi.com/bounty/forta). Please report any security issues you find through the Immunefi dashboard, or reach out to [[email protected]](mailto:[email protected])
+
+## Webhook
+
+To extend the client models with new fields, please do not modify generated code directly and instead
+
+1. update `protocol/webhook/swagger.yml`,
+2. do `make swagger`
+
+and the code will be regenerated by taking into account the latest shape of `swagger.yml`.