Add support for GeoJSON-L

[OmarShehata]

GeoJSONL: An optimized format for large geographic datasets

See: https://www.interline.io/blog/geojsonl-extracts/

Seems to be getting more support. It's basically GeoJSON but restructured to make it easy to stream. This is potentially an easy implementation that streamlines vector data in Cesium, and would be a great solution we can use today until vector 3D Tiles are further enough along. A lot of vector datasets I've seen on the forum aren't necessarily very large (a few thousand lines/polygons) but will completely freeze up the main thread in Cesium on load, or worse, crash. (This is something that the oldest open Cesium PR at the time of writing fixes but no consensus was reached #3970)

[OmarShehata]

@hpinkos propbably label "category - data sources" and "type - enhancement" ?

[mramato]

If this is all the rage and lots of users are asking for it, then it's a no-brainer, but unless I'm missing something, that's not currently the case.

I tried to google around for this but found very little info. Google itself only shows 195 hits for "geojsonl". I think we'll want to wait until this gains significant traction before implementing it, and while trivial, I am skeptical that this will provide any real improvement in Cesium because it will add a bunch of overhead.

It will certainly fix the lock-up issue caused by lack of incremental parsing, but the amount of time taken to load will be a lot higher and for large geometries, it will just move the problem to the primitive tessellation, which is the real bottleneck for formats like GeoJSON in 3D.

Not trying to be a downer, but I'm extremely skeptical here.