Consider an option to generate MikktSpace tangents

[donmccurdy]

The glTF specification recommends that loaders generate MikktSpace tangents when an asset needs tangents, but does not provide them. Unfortunately, I'm not aware of any JS implementation. Certainly an implementation could be ported from the canonical code, or generated with WASM, but (1) this adds loading overhead, and (2) the complexity of the code is comparable to that of the entire threejs glTF loader.

For those reasons, and because NodeJS can make use of native code more easily anyway, it would be a nice feature if glTF-Pipeline had an option to generate tangents.

Note that threejs previously ignored stored tangents and generated them in the shader, but the upcoming r102 release will support stored tangents.

[donmccurdy]

FYI on KhronosGroup/glTF#1252 (comment). If you're comfortable using WASM in gltf-pipeline, this could be added with https://github.com/donmccurdy/mikktspace-js.