add Bundler Perf section with tips?

[agilgur5]

Similar to the changes I made in the coverage branch, suggest people set noParse on ammo (or physijs-webpack/vendor/ammo in the external usage case) because it's gigantic and therefore slows down builds.

Not sure if there's a way to build that into the package as it's a bit annoying given the "out-of-the-box" experience this library is meant to give 🤔

Perhaps there are other bundler perf improvements too that I'm not aware of or don't realize