Fix mipmaps for 90%

[Displee]

I wasted a week on fixing mipmaps. You're not going to believe the fix 😡

However, there seems to be an issue with MeshLambertMaterial. When using that in the mipmaps example the mesh becomes black, but when using MeshBasicMaterial the textures work. Somehow MeshLambertMaterial is being treated differently.

I tried to update the MeshLambertMaterial class and set the default values like threejs does in r106, but I had no luck yet.

Forgive me for my useless "merge pull request" commits xD.

[Displee]

I added the kotlinx-io dependency because it's required for a Texture object to have a non-nulled image in order for it to render anything. Maybe you can add an EMPTY_IMAGE constant in the Texture class or something so you don't need the dependency in the examples module. What's your opinion on this matter?

[markaren]

I'm a little sidetracked at the moment. I promise to look at this next week!

[markaren]

Aight, I had a look. There was clearly a wrong use with texImage2D that you spotted. Good job.
For the MeshLambertMaterial case, simply add a light source :D