Add Draco encoder

[mkleins]

Draco is a powerful 3D library to compress 3D meshs: https://github.com/google/draco

What about Yoga compatibility? it could be a must to have.

[flozz]

• Draco is only supported as an extension to the glTF 2 format (KHR_draco_mesh_compression) by assimp. We may enable this extension through an option in YOGA.
• The Draco format itself (.drc files) is not supported by assimp yet, so it cannot be supported by YOGA for now.