readme fixes have been merged. thanks 
Probably, there is no document in Babylon.js that outlines what side effects to add
If you want es6 treeshaking,you’ll need to read the error messages on your own and find the appropriate side effects.It’s very helpful to download the Babylon.js source code locally and use source search to find dependency.
If you don’t think treeshaking is important, you can simply
import "@babylonjs/core";
as this will include all side effects that exist in Babylon.js.