Allow to return arbitrary `OverlayView` from the `MarkerClusterer.renderer.render`

[rtcpw]

The Renderer interface is declared as:

export interface Renderer {
    /**
     * Turn a {@link Cluster} into a `Marker`.
     *
     * Below is a simple example to create a marker with the number of markers in the cluster as a label.
     *
     * ```typescript
     * return new google.maps.Marker({
     *   position,
     *   label: String(markers.length),
     * });
     * ```
     */
    render(cluster: Cluster, stats: ClusterStats, map: google.maps.Map): Marker;
}

Please add the ability to return arbitrary OverlayView from the render function. The Marker type that render currently expects is deprecated. The render function needs to be updated to support the AdvancedMarkerElement, but it should also support arbitrary OverlayView as well.