message: filament.d.ts make init, fetch callbacks optional
diff: @@ -26,8 +26,8 @@ import * as glm from "gl-matrix";
  export as namespace Filament;
  export function getSupportedFormatSuffix(desired: string): void;
  -export function init(assets: string[], onready: () => void): void;
  -export function fetch(assets: string[], onready: () => void, onfetched: (name: string) => void): void;
  +export function init(assets: string[], onready?: (() => void) | null): void;
  +export function fetch(assets: string[], onDone?: (() => void) | null, onFetched?: ((name: string) => void) | null): void;
  export const assets: {[url: string]: Uint8Array};
  