added VCS webhook documentation links

runatlantis.io/contributing/events-controller.md

@@ -37,7 +37,22 @@ below-listed commands and, at last, the post-workflow hooks.
 
 ## Pull Request Event
 
-To handle comment events on Pull Requests, they must be created first. Atlantis also allows the running of commands for certain Pull Requests events.
+To handle comment events on Pull Requests, they must be created first. Atlantis
+also allows the running of commands for certain Pull Requests events.
+
+<details>
+  <summary>Pull Request Webhooks</summary>
+
+The list below links to the supported VCSs and their Pull Request Webhook
+documentation.
+
+- [Azure DevOps Pull Request Created](https://learn.microsoft.com/en-us/azure/devops/service-hooks/events?view=azure-devops#pull-request-created)
+- [BitBucket Pull Request](https://support.atlassian.com/bitbucket-cloud/docs/event-payloads/#Pull-request-events)
+- [GitHub Pull Request](https://docs.github.com/en/webhooks/webhook-events-and-payloads#pull_request)
+- [GitLab Merge Request](https://docs.gitlab.com/ee/user/project/integrations/webhook_events.html#merge-request-events)
+- [Gitea Webhooks](https://docs.gitea.com/next/usage/webhooks)
+</details>
+
 The following list shows the supported events:
 
 - Opened Pull Request