Add a horizontal scrolling shortcut of shift+scroll

[orangeisbetter]

In many other programs, it is standard for holding down shift while scrolling to scroll horizontally. Right now it just zooms out vertically, which I feel is unintuitive. Especially for longer songs, dragging the scroll bar with a mouse can make it very difficult to look at the part of the song you want to see.

[GabrielMiceli]

The shortcut for that is Alt+Scroll. Unfortunately, it's like that for most Qt applications, and it irritates me also.

[orangeisbetter]

Are you serious? This has been in there the whole time? Thanks for telling me this.