wrap interfaces in a module

After Kon-san wrote gamepad.d.ts, Gamepad API's Interface has updated.
In current version, Gapepad.buttons' type is not number[] but GamepadButton[].
( http://www.w3.org/TR/gamepad/)
So, I would like to add GameButton interface to gamepad.d.ts.

Before I do so, I would also like to ask committers and Kon-san whether can I change namespace design or not.
I prefer wrapping interfaces in a module to writing in global scope.
I executed "npm update && npm run all" and had no errors.

If there is some reason that I don't notice, could you tell me.
I'll add GameButton interface to Kon-san's version.