docs: add info about voice-channel support

Author: lkuechler

README.md

@@ -27,6 +27,10 @@ This repository contains configurations and instructions that can be used for de
 > [!NOTE]
 > amd64 builds are not currently available for the web client.
 
+> [!NOTE]
+> This guide does not include the instructions for setting up [vortex](https://github.com/revoltchat/vortex), which is a requirement for voice channels.
+> Community-created documentation for setting it up is available in this pull request but not recommended: <https://github.com/revoltchat/self-hosted/pull/114>
+
 ## Table of Contents
 - [Deployment](#deployment)
 - [Updating](#updating)