function init() {
    const initialPosition = { lat: 25.00, lng: 71.00 };
    const map = createMap(initialPosition);
    const marker = createMarker({ map, position: initialPosition });

    let watchId = trackLocation({
        onSuccess: ({ coords: { latitude: lat, longitude: lng } }) => {
            marker.setPosition({ lat, lng });
            map.panTo({ lat, lng });
            
        },
        onError: err => {
            console.log($info);
            $info.textContent = `Error: ${err.message || getPositionErrorMessage(err.code)}`;
            $info.classList.add('error');
        }
    });
}
Initialize the application.
Automatically called by the google maps API once it's loaded.