TS: Fix material and geometry declaration of Sky.

examples/jsm/objects/Sky.d.ts

@@ -1,11 +1,16 @@
 import {
-	Mesh
+	BoxBufferGeometry,
+	Mesh,
+	ShaderMaterial
 } from '../../../src/Three';
 
 export class Sky extends Mesh {
 
 	constructor();
 
+	geometry: BoxBufferGeometry;
+	material: ShaderMaterial;
+
 	static SkyShader: object;
 
 }