Need better examples for vertex shaders in 3d meshes

Currently we have one example showing how to write a vertex shader, and that example is for 2d meshes. Most custom shader examples only define a fragment shader, and use the default vertex shader. I'd like to see examples of vertex shaders for 3d meshes.

A good example should show:

* What does the vertex input data look like?
* What does the vertex output data look like?
* What are the minimum calculations that need to happen (position and normal calculation, etc.)
* For extended materials, what calculations can be skipped because they are already done in the base material? Assume that we're using StandardMaterial as a base.