Add a note to simplify comments for vertex buffer compaction
Add a note to simplify comments for vertex buffer compaction

While it's common to still require the original vertex buffer for use
with fine LOD, sometimes pure simplification is desireable in which case
it's possible to use meshopt_optimizeVertexFetch (which will compact the
required vertex data and return the number of vertices used).

Fixes #15.

zeux/meshoptimizer,zeux/meshoptimizer,zeux/meshoptimizer