As part of #216, create a Playlist class:
- "open", "close", "toggle" functions
- it loads the tracks from the backend and it does not depend on
Ajaxify.get() to do so.
- it uses them to build the list
- it handles keyboard arrows for highlighting tracks
- it handles ENTER for playing the highlighted track
- it handles SPACE for playing a track globally
- it manages the search field
- auto scrolls when opened
As part of #216, create a Playlist class:
Ajaxify.get()to do so.