Glyph support

[Shuggreal]

I'm not sure what it would do exactly but its only natural for Glyph support.

[cyanChill]

Glyph support would probably just be a "rave" with lights. Nothing OS has a Music Visualization (they spelt it as visualisation) option that you can toggle.

Currently, it doesn't work with this app because we don't play audio through the music notification (that's how the visualization works I assume; even though it claims it works for audio played through the speakers, it really means audio played though the music notification).

After the v1.0.0 release, I plan on refactoring the code so it does go through the notification (we didn't do this initially because I didn't want to figure it out at the time how to dynamically update the list of tracks through the notification, since we're using a package that abstracts that logic and that its "simpler" in the way we currently do it).