Change default compression with 'optimize' CLI to Meshopt

[donmccurdy]

I've come to the conclusion that Meshopt might be the better default for the 'optimize' command. It's much faster to decode, requires a smaller decoder, and avoids some tricky problems like:

• https://github.com/donmccurdy/glTF-Transform/issues/1343
• https://github.com/donmccurdy/glTF-Transform/issues/1370
• https://github.com/donmccurdy/glTF-Transform/issues/1342
• https://github.com/donmccurdy/glTF-Transform/issues/1215
• https://github.com/donmccurdy/glTF-Transform/issues/1098