dispatchEvent in wheelCallback (#494)

Author: AlaricBaraou

src/three/controls/EnvironmentControls.js

@@ -369,6 +369,8 @@ export class EnvironmentControls extends EventDispatcher {
 
 			e.preventDefault();
 
+			this.dispatchEvent( _startEvent );
+
 			let delta;
 			switch ( e.deltaMode ) {
 
@@ -390,6 +392,8 @@ export class EnvironmentControls extends EventDispatcher {
 			this.zoomDelta -= 3 * deltaSign * normalizedDelta;
 			this.needsUpdate = true;
 
+			this.dispatchEvent( _endEvent );
+
 		};
 
 		const pointerenterCallback = e => {