Expand requirements sentence into document section

doc/quick-install.md

@@ -2,7 +2,16 @@
 
 This guide helps you  ___host your own Jitsi server___. If you want to have a video conference without setting up any infrastructure, use https://meet.jit.si instead.
 
-This document describes the required steps for a quick Jitsi Meet installation on a Debian based GNU/Linux system. Debian 8 (Jessie) or later, and Ubuntu 14.04 or later are supported out-of-the-box.
+## Requirements
+
+The installation steps documented here are intended for Debian-based GNU/Linux systems.
+
+Systems running the following versions are supported by this guide:
+
+1. Debian 8 (Jessie) or later
+1. Ubuntu 14.04 or later
+
+To check the operating system available, you can run `cat /etc/issue` at the command-line.
 
 Debian Wheezy and other older systems may require additional things to be done. Specifically for Wheezy, [libc needs to be updated](http://lists.jitsi.org/pipermail/users/2015-September/010064.html).