Add description for Developers/webhook page (#6327)

- Add optional description field to webhook page in developer settings.

Fix https://github.com/twentyhq/twenty/issues/6236

---------

Co-authored-by: Thomas Trompette <thomas.trompette@sfr.fr>

packages/twenty-front/src/modules/settings/developers/types/webhook/Webhook.ts

@@ -1,6 +1,7 @@
 export type Webhook = {
   id: string;
   targetUrl: string;
+  description?: string;
   operation: string;
   __typename: 'Webhook';
 };