Easier deck.gl debugging for Lonboard issues

In https://github.com/developmentseed/lonboard/pull/562#issuecomment-2229473126 we're hitting a deck.gl bug when trying to upgrade from deck.gl v8 to v9. The upstream issue was closed and believed to be fixed. So we need to provide a reproducible, minimal example, but we can't ask deck.gl contributors to learn Python and learn Lonboard.

We should have some documentation and/or testing utils to help construct a minimal JS app using data and layers exported from a Lonboard `Map` object.