Add middle-click + drag listener for ZOOM on EnvironmentControls

Is your feature request related to a problem? Please describe.

The EnvironmentControls parses left and right clicks + mouse-wheel events, (Quick note, the SHIFT + LEFT_CLICK did not trigger rotate during my tests). It could be nice if these controls could also parse Middle click for zoom - the awy it is done in googleMapsAerial within OrbitControls

Describe the solution you'd like

Web/API/Pointer_events suggest adding to PointerTracker.js

isMiddleClicked() {
  return Boolean( this.buttons & 4 );
}

And then this could probably resort to something like the following addition to EnvironmentControls.js - pointerdownCallback

else if ( pointerTracker.isMiddleClicked() ) {

	// if the clicked point is coming from below the plane then don't perform the drag
	this.setState( ZOOM );
	this.zoomDirectionSet = false;
	this._updateZoomDirection();

        // The below could be shared on top if the `if (hit)` block
        this.pivotPoint.copy( hit.point );
        this.pivotMesh.position.copy( hit.point );
        this.pivotMesh.updateMatrixWorld();
        this.scene.add( this.pivotMesh );
}

Finally,

• or replicate somehow the wheelCallback and replace how it handles event cursor e.deltaY motion with movementY, and apply to zoomDelta, but build this into pointermoveCallback:

	const pointermoveCallback = e => {
	// ...
	// Add mouse click handle in pointerMove
	if ( this.state === ZOOM ) {

		console.log( 'MOUSE MIDDLE CLICKED: ', e, e.deltaMode, e.deltaY );
		const delta = e.movementY;
		// use LOG to scale the scroll delta and hopefully normalize them across platforms
		const deltaSign = Math.sign( delta );
		const normalizedDelta = Math.log( Math.abs( delta ) + 1 );
		this.zoomDelta -= 3 * deltaSign * normalizedDelta * 1;
		// this.needsUpdate = true;

	}

Describe alternatives you've considered

Use another controls, like Pivot controls instead of EnvironmentControls to handle middle-mouse click

Start with PointerTracker.js and EnvironmentControls.js, especially pointerdownCallback, pointermoveCallback, and wheelCallback. Compare the existing behavior with OrbitControls in the linked googleMapsAerial example, then verify that middle-button dragging zooms around the selected pivot without changing existing click or wheel controls. Check the project’s existing examples or tests for regressions.