Add file extensions to legacy import paths

src/Three.Legacy.js

@@ -20,12 +20,12 @@ import {
 } from './core/BufferAttribute.js';
 import { BufferGeometry } from './core/BufferGeometry.js';
 import { Face3 } from './core/Face3.js';
-import { Geometry } from './core/Geometry';
+import { Geometry } from './core/Geometry.js';
 import { Object3D } from './core/Object3D.js';
-import { Uniform } from './core/Uniform';
+import { Uniform } from './core/Uniform.js';
 import { Curve } from './extras/core/Curve.js';
 import { CatmullRomCurve3 } from './extras/curves/CatmullRomCurve3.js';
-import { BoxHelper } from './helpers/BoxHelper';
+import { BoxHelper } from './helpers/BoxHelper.js';
 import { GridHelper } from './helpers/GridHelper.js';
 import { SkeletonHelper } from './helpers/SkeletonHelper.js';
 import { BoxGeometry } from './geometries/BoxGeometry.js';