Mute Shortcuts per egvl

Similar to Chrome and Safari mute options.
Unintrusive and simple to use.
Now you can:
- Mute/Unmute all audible tabs (ctrl+shift+M)
- Mute/Umnute a specific site (ctrl+shift+i) or (right click tab)
- Cicle through your audible tabs (ctrl+shift+L)
- Unmute/reset all tabs (ctrl+shift+U)
- Open link in new muted tab (right click link)

Code available at: https://github.com/egvl/MuteShortcuts