Update documentation

doc/user/project/integrations/discord_notifications.md

+# Discord Notifications service
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/22684) in GitLab 11.5.
+
+The Discord Notifications service sends notifications from GitLab to the channel for which the webhook was created.
+
+## On Discord
+
+1. Open the channel in which you want to see the notifications.
+1. From the channel menu, select **Edit channel**.
+1. Click on **Webhooks** menu item.
+1. Click on **Create Webhook** and fill in the name of the bot that will post the messages. Optionally define avatar.
+1. Copy the **WEBHOOK URL** of your webhook and click **Save**.
+
+See also [Intro to Webhooks](https://support.discordapp.com/hc/en-us/articles/228383668-Intro-to-Webhooks) article. 
+
+## On GitLab
+
+When you have the **Webhook URL** for your Discord Notifications channel webhook, you can set up the GitLab service.
+
+1. Navigate to the [Integrations page](project_services.md#accessing-the-project-services) in your project's settings, i.e. **Project > Settings > Integrations**.
+1. Select the **Discord Notifications** project service to configure it.
+1. Check the **Active** checkbox to turn on the service.
+1. Check the checkboxes corresponding to the GitLab events you want to receive.
+1. Paste the **Webhook URL** that you copied from the Discord Notifications configuration step.
+1. Configure the remaining options and click `Save changes`.
+
+Your Discord Notifications channel will now start receiving GitLab event notifications as configured.
+
+![Discord configuration](img/discord_notifications_configuration.png)

doc/user/project/integrations/project_services.md

@@ -30,6 +30,7 @@ Click on the service links to see further configuration instructions and details
 | [Bugzilla](bugzilla.md) | Bugzilla issue tracker |
 | Campfire | Simple web-based real-time group chat |
 | Custom Issue Tracker | Custom issue tracker |
+| [Discord Notifications](discord_notifications.md) | Receive event notifications in Discord |
 | Drone CI | Continuous Integration platform built on Docker, written in Go |
 | [Emails on push](emails_on_push.md) | Email the commits and diff of each push to a list of recipients |
 | External Wiki | Replaces the link to the internal wiki with a link to an external wiki |