change init root to window
change init root to window

VANITAX/PhysicsJS,jpellerin/PhysicsJS,mcanthony/PhysicsJS,haithemaraissia/PhysicsJS,haithemaraissia/PhysicsJS,griever989/PhysicsJS,wellcaffeinated/PhysicsJS,Luwdo/PhysicsJS,mcanthony/PhysicsJS,Nayar/PhysicsJS,rohit765/PhysicsJS,jpellerin/PhysicsJS,griever989/PhysicsJS,Nayar/PhysicsJS,Luwdo/PhysicsJS,rohit765/PhysicsJS,eric-seekas/PhysicsJS,Rawneed/PhysicsJS,pietro909/PhysicsJS,VANITAX/PhysicsJS,Rawneed/PhysicsJS,pietro909/PhysicsJS,eric-seekas/PhysicsJS,wellcaffeinated/PhysicsJS