Add support for retrieving TileJSON metadata

[MateoV]

https://www.mapbox.com/api-documentation/#retrieve-tilejson-metadata

This would allow us to display and use information about a tileset in the Editor for things like:

• selecting layers to send to mesh factories
• styling and filtering features based on properties
• utilizing zoom range/bounds/center of the tileset
• displaying description of map/layers/properties

Currently we have to know all of these things beforehand and manually code which layers we want to generate and what properties we want to display or filter on. The idea is to input a mapid in the editor and have it fetch and show this metadata. Will make a separate ticket about editor functionality in the main sdk repo.

[david-rhodes]

@MateoV Are you thinking the primary use case is for design-time?