Loading spinner till the loaded dataset appears on the map

Firstly, thanks for this marvelous work! I have a question that I hope someone can help me with.

I have a React app in which I mounted Kepler and load a dataset into `addDataToMap` function. When I run the app, the modal of `Add data` below appears for a few moments until the data appears on the map correctly.

1. Is there a way to change the content in this modal like for example to add a loading spinner? or is there a function or property to override it in order to do so?

Start by tracing the addDataToMap flow and the Add data modal mentioned in the issue to determine where loading state and modal content are controlled. Done would be a clearly supported way to show a loading spinner or override that modal while the dataset is being loaded.

Written by the indexing model from the issue text.