allow adjusting volume with scrolling

[SamiSuleiman]

@adsuth @ynshung Please let me know if I made any mistakes <3

[adsuth]

Looks good to me, one thing I'd change is the increment. If you were to make it a bit smaller, the scroll would be a lot more smooth and feel better I think

Theres actually a global for the increment amount called VOLUME_INCREMENT_AMOUNT which would ideally be used instead for consistency (if we want to, say, allow a user to change it later down the line)