Allow for export with built-in environment map

[dsinni]

I'm not sure how difficult this would be with the current spec, but it would be great if models could be exported with built-in environment maps.

Adding environment maps in some engines/frameworks can be a cumbersome task, especially for those who are not coders. For those who use 3D software for most of their workflow, it seems that exporting the environment with the model may make the most sense, if it's possible.

Just for reference, to quote @emackey:

Not from Blender, currently. Adobe Dimension has that capability, at least internally when publishing to web. They haven't exposed a direct export button though.

It would be great to see this as an export option, possibly utilizing an extension.

Would love your feedback on this.

Thanks!