help: Document quick way to check Zulip version.

Version number was added to top section of gear menu in
4df8c6610f.

Version number was added to "About Zulip" in
668b5137b0.

help/view-zulip-version.md

@@ -10,13 +10,25 @@ web app your organization is using.
 Zulip Cloud organizations are always updated to the latest version of Zulip.
 
 [upgrade-zulip]:
-    https://zulip.readthedocs.io/en/stable/production/upgrade-or-modify.html
+    https://zulip.readthedocs.io/en/latest/production/upgrade-or-modify.html
-[changelog]: https://zulip.readthedocs.io/en/stable/overview/changelog.html
+[changelog]: https://zulip.readthedocs.io/en/latest/overview/changelog.html
 
 ### View Zulip server and web app version
 
 {start_tabs}
 
+{tab|v6}
+
+1. Click on the **gear** (<i class="fa fa-cog"></i>) icon in the upper
+   right corner of the web or desktop app.
+
+1. View the version number or Zulip Cloud plan in the top section of the menu.
+
+1. *(optional)* Click on the version number or Zulip Cloud plan for additional
+   details.
+
+{tab|v4}
+
 {relative|gear|about-zulip}
 
 1. View the version number under **Zulip Server**.

zerver/lib/markdown/tabbed_sections.py

@@ -98,6 +98,8 @@ TAB_SECTION_LABELS = {
     "via-compose-box-buttons": "Via compose box buttons",
     "stream-compose": "Compose to a stream",
     "dm-compose": "Compose a DM",
+    "v6": "Zulip Server 6.0+",
+    "v4": "Zulip Server 4.0+",
 }