Make use of intersection observer to delay on first load

[Tim van der Lippe]

Often times, the google maps element is not visible on the first page load/above the fold. It would be nice to that instead of executing in attached, the element is initialized when the element is in viewport. An intersection observer can be used to trigger the initialization (if the browser supports it). Possibly it could also lazy-load the google-apis, instead of eagerly loading.