[FEATURE] Add "show song info"

[xxxserxxx]

Add the ability to show song metadata available through the Subsonic API.

I'm thinking something like a vertical split tab in the Queue, where the currently highlighted song's metadata is shown as a simple key/value list. This would be the bare minimum; enhancements could include:

• Showing rasterized cover art
• Toggle the split

[spezifisch]

Showing rasterized cover art

Do you notice any sluggishness when scrolling through the queue?
It takes about 1-3 seconds to select the next entry.

[xxxserxxx]

Do you notice any sluggishness when scrolling through the queue? It takes about 1-3 seconds to select the next entry.

Hmm. I haven't. However, this would not be fork into a background process to pre-fetch all of the images in the queue. Although it wasn't intentional, the way I implemented this with the caching should make it relatively easy to implement.

I'll add another ticket.

[spezifisch]

Reference (after closing the linked thread): #29

[xxxserxxx]

PR #66 should address the scrolling issues with image fetching latencies. If that's accepted and merged, this can be closed; if we want to add more stuff to the song info panel (e.g. lyrics) they should be separated tickets.