tracks appear empty when viewing a very large region -- add "zoom in to view"

[ChangxuFan]

The last track in the view [added via Tracks -> annotation tracks -> JASPAR 2022] appears to be empty. This is because the viewing region is too big: it's actually not empty when zooming in to a small region.

It would be helpful to say "Region too large: Zoom in to view" so that the users know the track is working. This is the behavior of the 2022 browser.

Best,
Fan