Update the build instructions for mp3 support

to reflect the default change for mp3 support from mad to mpg123

readme.md

@@ -102,12 +102,12 @@ To compile vkQuake, first install the build dependencies:
 
 Ubuntu:
 ~~~
-apt-get install git meson gcc glslang-tools spirv-tools libsdl2-dev libvulkan-dev libvorbis-dev libmad0-dev libx11-xcb-dev
+apt-get install git meson gcc glslang-tools spirv-tools libsdl2-dev libvulkan-dev libvorbis-dev libmpg123-dev libx11-xcb-dev
 ~~~
 
 Arch Linux:
 ~~~
-pacman -S git meson flac glibc libgl libmad libvorbis libx11 sdl2 vulkan-headers glslang spirv-tools
+pacman -S git meson flac glibc libgl mpg123 libvorbis libx11 sdl2 vulkan-headers glslang spirv-tools
 ~~~
 
 Then clone the vkQuake repo:
@@ -139,7 +139,7 @@ meson build && ninja -C build
 To compile vkQuake, first install the build dependencies with Homebrew:
 
 ~~~
-brew install molten-vk vulkan-headers glslang spirv-tools sdl2 libvorbis flac opus opusfile flac mad meson pkgconfig
+brew install molten-vk vulkan-headers glslang spirv-tools sdl2 libvorbis flac opus opusfile flac mpg123 meson pkgconfig
 ~~~
 
 Then clone the vkQuake repo: