WIP: Moving from webpack to rollup, attempt 2

[0b5vr]

will close #502 , will close #144
Retry of #506

• Changed the bundler, from webpack to rollup
• 🚨 .module.js is now esm instead of umd
  • You are going to need es-module-shims if you want to use module build without bundlers! See the updated README.md for details
    • We are going to continue providing UMD versions for now. See: Examples: Removed deprecation warning. mrdoob/three.js#20568
• Updated README and examples accordingly
• In IIFE variant, VRM components are installed under THREE_VRM
  • Also be installed under THREE as previous

Need to check

• Does this work with npm using bundlers?
• Need to check the spec of import-maps again
  • We don't have to secure this for now because its still drafter than we thought. See: Examples: Removed deprecation warning. mrdoob/three.js#20568
• How about separated components in future?
  • Monorepo seems to be working good

[0b5vr]

It seems we cannot drop iife and cjs output yet...... 😩

mrdoob/three.js#20568