feat: Add Share option for artists, albums, and tracks

This feature is only available on the Subsonic media provider. Using a
Jellyfin server will make Supersonic hide the "Share" option.

* Artists: Option available in grid view and in Artist view.
* Albums: Option available in grid view and in Album view.
* Tracks: Option available in tracklist, when a single track is selected.

ui/browsing/favoritespage.go

@@ -395,7 +395,9 @@ func (a *FavoritesPage) onShowFavoriteSongs() {
 			}
 			tracklist.Options = widgets.TracklistOptions{AutoNumber: true}
 			_, canRate := a.mp.(mediaprovider.SupportsRating)
+			_, canShare := a.mp.(mediaprovider.SupportsSharing)
 			tracklist.Options.DisableRating = !canRate
+			tracklist.Options.HideSharing = !canShare
 			tracklist.SetVisibleColumns(a.cfg.TracklistColumns)
 			tracklist.SetSorting(a.trackSort)
 			tracklist.OnVisibleColumnsChanged = func(cols []string) {