Export ImageOverlay and TiledImageOverlay (#1567)

Author: xawill

src/three/plugins/images/ImageOverlayPlugin.js

@@ -1276,7 +1276,7 @@ export class ImageOverlayPlugin {
  * @param {boolean} [options.alphaInvert=false] If true, inverts the alpha channel before
  * applying the mask or blend.
  */
-class ImageOverlay {
+export class ImageOverlay {
 
 	get isPlanarProjection() {
 
@@ -1389,7 +1389,7 @@ class ImageOverlay {
  * multiple source tiles into a single texture per 3D tile region.
  * @extends ImageOverlay
  */
-class TiledImageOverlay extends ImageOverlay {
+export class TiledImageOverlay extends ImageOverlay {
 
 	get tiling() {