An example of using the 'react-leaflet' new useLeaflet() hook?

First of all, you can only use the hook in a component that's inside the Map element:

<Map>
  <YourComponent />
</Map

And then inside your component you can do something like:

const YourComponent = () => {
  const { map } = useLeaflet();
  const [bounds, setBounds] = React.useState({});

  React.useEffect(() => {
    const eventHandler = event => {
      setBounds(event.target.getBounds());
      doSomethingElse();
    }
    map.on("moveend", eventHandler);

    return () => {
      map.off("moveend", eventHandler); // Remove event handler to avoid creating multiple handlers
    }
  }, [setBounds, map]);

  return {
    // Use bounds for whatever you need
    <div>Lat: {bounds.lat}; long: {bounds.lng}</div>
  }
}