Referencing of other asset files, scene description, instancing of objects

[LudwigFriedmann]

Is your feature request related to a problem? Please describe.
In #117, a potential need to reference other asset files was identified.

It has to be clarified if the development of a concept for this topic is possible for release 1.0 of OpenMATERIAL.

This issue can be extended to scene description and instancing of objects.

Example:

Describe the solution you'd like
Develop a concept for asset referencing / scene description. Achieve alignment with other ASAM standards (ASAM OpenSCENARIO, Open Simulation Interface etc.).

Describe alternatives you've considered

Additional context