Support Standard (Roughness setup)

[yangfawen]

We want to support Standard (Roughness setup) material.

[AurL]

Hi @yangfawen

Sorry for being very late here.
This Unity material update has been missed.

Also, please note that this plugin is not longer maintained, as we moved to https://github.com/sketchfab/UnityGLTF

I'm working on a small update there, so I will include the fix to support this "new" material type.

Thanks!