Allow authorization using `clientID` instead of `apiKey`
Allow authorization using `clientID` instead of `apiKey`

This commit will make `apiKey` in the constructor optional.

When using Google Maps Platform Premium Plan,
it is possible to authorize using `clientID` only.

See more on [official documentation]

[official documentation]: https://developers.google.com/maps/documentation/javascript/error-messages#key-looks-like-client-id

Carrooi/Js-GoogleMapsLoader,Carrooi/Node-GoogleMaps,Carrooi/Node-GoogleMaps,Carrooi/Js-GoogleMapsLoader