adding webhook example to show sucessful install

Author: alexcoderabbitai

docs/platforms/gitlab-com.md

@@ -76,3 +76,9 @@ GitLab provides an option to generate a personal access token for a new user. Fo
 3. Click **Install Repositories**.
 
 ![GitLab repo Installation](/img/integrations/gitlab-repo-install.png)
+
+4. After this step you will see the `https://coderabbit.ai/gitlabHandler` webhook installed in your repositories.
+
+![GitLab Webhook Example](/img/integrations/gitlab-webhook.png)
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+