help: Add "Follow a topic" page.

Co-authored-by: David <rosatamsen@gmail.com>

help/follow-a-topic.md

@@ -0,0 +1,53 @@
+# Follow a topic
+
+Zulip lets you follow topics you are interested in. You can configure how you get notified about new messages for topics you follow.
+
+In muted streams, topics you follow are automatically treated as
+[unmuted](/help/mute-a-topic).
+
+## Follow or unfollow a topic
+
+{start_tabs}
+
+{tab|desktop-web}
+
+{!topic-actions.md!}
+
+1. Configure topic notifications using the row of icons at the top of the menu.
+
+!!! tip ""
+
+    You can also configure notifications by clicking the topic notifications status
+    icon in the message recipient bar or in **Recent conversations**.
+
+{end_tabs}
+
+## Configure notifications for followed topics
+
+{start_tabs}
+
+{settings_tab|notifications}
+
+1. In the **Notification triggers** table,
+   toggle the settings for **Followed topics**.
+
+{end_tabs}
+
+## Manage configured topics
+
+{start_tabs}
+
+{tab|desktop-web}
+
+{settings_tab|topics}
+
+1. Configure notifications for each topic by selecting the desired option from
+   the dropdown in the **Status** column.
+
+{end_tabs}
+
+## Related articles
+
+* [Stream notifications](/help/stream-notifications)
+* [Mute or unmute a topic](/help/mute-a-topic)
+* [Mute or unmute a stream](/help/mute-a-stream)

help/include/sidebar_index.md

@@ -138,6 +138,7 @@
 
 ## Notifications
 * [Stream notifications](/help/stream-notifications)
+* [Follow a topic](/help/follow-a-topic)
 * [DMs, mentions, and alerts](/help/dm-mention-alert-notifications)
 * [Mute or unmute a stream](/help/mute-a-stream)
 * [Mute or unmute a topic](/help/mute-a-topic)

help/mute-a-topic.md

@@ -13,4 +13,5 @@
 ## Related articles
 
 * [Mute or unmute a stream](/help/mute-a-stream)
+* [Follow a topic](/help/follow-a-topic)
 * [Mute a user](/help/mute-a-user)