Add LUTCubeLoader dts

examples/jsm/loaders/LUTCubeLoader.d.ts

+import {
+	Loader,
+	LoadingManager,
+	Vector3,
+	DataTexture,
+	DataTexture3D,
+} from '../../../src/Three';
+
+export interface LUTCubeResult {
+
+	title: string;
+	size: number;
+	domainMin: Vector3;
+	domainMax: Vector3;
+	texture: DataTexture;
+	texture3D: DataTexture3D;
+
+}
+
+export class LUTCubeLoader extends Loader {
+
+	constructor( manager?: LoadingManager );
+
+	load(
+		url: string,
+		onLoad: ( result: LUTCubeResult ) => void,
+		onProgress?: ( event: ProgressEvent ) => void,
+		onError?: ( event: Error ) => void
+	);
+	parse( data: string ): LUTCubeResult;
+
+}