fix(user): Add desktop and mobile client mention to Talk index page

Reference nextcloud.com/install for desktop (Windows, macOS, Linux)
and mobile (Android, iOS) client downloads.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Signed-off-by: Maksim Sukharev <antreesy.web@gmail.com>

Author: Antreesy

user_manual/talk/index.rst

@@ -2,10 +2,11 @@
 Talk
 ====
 
-Nextcloud Talk offers audio/video and text chat integrated in Nextcloud. It offers
-a web interface as well as mobile apps.
+Nextcloud Talk offers audio/video and text chat integrated in Nextcloud. It is
+available as a web interface, desktop client, and mobile apps for Android and iOS.
 
 You can find out more about Nextcloud Talk `on our website <https://nextcloud.com/talk/>`_.
+Download the desktop and mobile clients from `nextcloud.com/install <https://nextcloud.com/install/>`_.
 
 .. image:: images/talk-grid-view.png