Tree shaking and bundle size

[paarthenon]

Evaluate how well the library can be tree-shaken. While the library is already pretty small (3kb gzipped) this would be nice to have, especially since many users are likely unaware of the advanced functionality of Variant (flags/matrix, type-first elements) and if they aren't using them, they might as well not spend the kb.

Other discriminants

I have a sneaking suspicion that variantCosmos, as convenient as it is from a UX perspective, will significantly complicate tree-shaking. Let's find out.