Add @mml-io/model-loader

[MarcusLongmuir]

This PR adds a new package, @mml-io/model-loader, that exposes a ModelLoader class that can:

• Load gTLF, GLB, and FBX
• Load from URL
• Load from a buffer
• Load DRACO-compressed gLTF

Exposing this class as a package enables reuse of the model loading capability currently used in the MML library (most crucially DRACO without having to load the web assembly files remotely).

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What kind of changes does your PR introduce? (check at least one)

• [x] Feature

Does your PR introduce a breaking change? (check one)

• [x] No

Does your PR fulfill the following requirements?

• [x] All tests are passing