[Req] Volume Hotkey with OSD

[laukond]

In-game you can bind a key to 'Master Volume Up/Down'.
I'd love an Addon that, when the volume is changed, displays the new value (eg. Volume 30%) on the screen for 2 seconds. If the volume is changed within these 2 seconds, the old value should dissapear and display the new value (eg. Volume 20%).
The center of the screen seems like a good position.