[BUG] Layer Attribution Option

[wildintellect]

Context

What results were you expecting?

Some external layers require attribution as part of their licensing and terms of use. Many mapping libraries implement this as an attribution key on a layer definition that becomes a rendered over the map static text (sometimes HTML is supported).

BaseMap Layers might already have this specified in their style json, but will likely come up with many layer types particularly BitMapTileLayer where an external XYZ tile service is used.
https://maplibre.org/maplibre-style-spec/sources/#attribution
https://maplibre.org/maplibre-gl-js/docs/API/classes/AttributionControl/

This may not be a critical feature for users viewing their own notebooks, but will be an issue as they shared rendered notebooks or export images.

[kylebarron]

This is somewhat related to ideas I've had about letting users add to the underlying Maplibre map, e.g. through custom basemap styles #494. But there's also a question of how tied Lonboard should be to Maplibre. It makes some things like this simpler but also makes other things harder, because tying us to maplibre ties us to Web Mercator