Alphabet "jump to" index

[RainbowPants]

Great player first of all! one feature I miss greatly after switching from musicbee is the jump-to index in album view, so if you sort by Album Artist/Album for example in that view and press "R" you would jump to the first album artist starting with R. It's really amazing for navigating large libraries. Maybe wouldn't be too hard to implement either? Looks like so:

[jeffvli]

Definitely think this is a valuable feature to add. I'll look into it for the next version.