Allow applying a shader to a raster layer.

Nobody has claimed this yet.

Asking to allow us to apply a shader to a specific raster layer. This would open up a lot of possibilities that are not currently possible. This would work how I imagine the Hillshade Layer works and also as shown in mapbox-gl-js

https://github.com/mapbox/mapbox-gl-js/blob/7dec10fe9c1a9a5a7ddf1116dbf03345026245bc/src/shaders/hillshade.fragment.glsl

Examples of use with DEM raster imagery:

- Replicate what Shademap is doing on device - https://shademap.app/@47.0949,15.5751,15z,1719305813809t,0b,0p,0m
- Sea level rise using DEM raster data as shown in this mapbox-gl-js example https://dnomadb.github.io/shader/#6.47/37.527/-122.114
- Indicate different snow heights at different elevations

I imagine there could be quite a few use cases with custom Raster data and Satellite imagery as well

Review the existing Hillshade Layer behavior and the linked mapbox-gl-js hillshade fragment shader first; no repository files or tests are named in the issue. Establish the scope for applying a custom shader to one raster layer, then validate it against the DEM examples: hillshade, sea-level rise, and elevation-based snow visualization.

Written by the indexing model from the issue text.