TS: Clean up.

src/loaders/ImageBitmapLoader.d.ts

 import { Loader } from './Loader';
-import { LoadingManager } from './LoadingManager.js';
+import { LoadingManager } from './LoadingManager';
 
 export class ImageBitmapLoader extends Loader {
 

src/math/SphericalHarmonics3.d.ts

-import { Vector3 } from './Vector3.js';
+import { Vector3 } from './Vector3';
 
 export class SphericalHarmonics3 {
 

src/renderers/webgl/WebGLTextures.d.ts

-import { WebGLExtensions } from './WebGLExtensions.js';
-import { WebGLState } from './WebGLState.js';
-import { WebGLProperties } from './WebGLProperties.js';
-import { WebGLCapabilities } from './WebGLCapabilities.js';
-import { WebGLUtils } from './WebGLUtils.js';
-import { WebGLInfo } from './WebGLInfo.js';
+import { WebGLExtensions } from './WebGLExtensions';
+import { WebGLState } from './WebGLState';
+import { WebGLProperties } from './WebGLProperties';
+import { WebGLCapabilities } from './WebGLCapabilities';
+import { WebGLUtils } from './WebGLUtils';
+import { WebGLInfo } from './WebGLInfo';
 
 export class WebGLTextures {