Update babylon.d.ts
Update babylon.d.ts

BABYLON.AbstractMesh.clone() method's "newParent: Node" argument made optional to match the documentation. Previously it was required, and the TypeScript compiler enforced a Node type be passed when cloning an AbstractMesh.
Temechon/Babylon.js,Kesshi/Babylon.js,Hersir88/Babylon.js,jbousquie/Babylon.js,RaananW/Babylon.js,BabylonJS/Babylon.js,jbousquie/Babylon.js,RaananW/Babylon.js,Kesshi/Babylon.js,NicolasBuecher/Babylon.js,abow/Babylon.js,sebavan/Babylon.js,sebavan/Babylon.js,BabylonJS/Babylon.js,Hersir88/Babylon.js,abow/Babylon.js,sebavan/Babylon.js,Hersir88/Babylon.js,Temechon/Babylon.js,Kesshi/Babylon.js,NicolasBuecher/Babylon.js,Temechon/Babylon.js,abow/Babylon.js,jbousquie/Babylon.js,BabylonJS/Babylon.js,RaananW/Babylon.js,NicolasBuecher/Babylon.js