Allow null in WebGLRenderer's setOpaqueSort & setTransparentSort

[iv-rid]

In WebGLRenderer, in both setOpaqueSort and setTransparentSort:

null is a valid value of the method argument. But null is missing in the type information.

/**
 * Sets the custom opaque sort function for the WebGLRenderLists. Pass null to use the default painterSortStable function.
 */
setOpaqueSort(method: (a: any, b: any) => number): void;

/**
 * Sets the custom transparent sort function for the WebGLRenderLists. Pass null to use the default reversePainterSortStable function.
 */
setTransparentSort(method: (a: any, b: any) => number): void;