Add marker library support

[jeantimex]

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Is your feature request related to a problem? Please describe.
With the release of Advanced Markers, a new marker library is also introduced. To allow us to use the new Advanced Markers API (including both AdvancedMarkerView and PinView, we need to specify marker in the libraries prop.

Describe the solution you'd like
We should be able to add marker in the libraries prop:

import { Loader } from '@googlemaps/js-api-loader';

const loader = new Loader({
  apiKey: "",
  version: "beta",
  libraries: ["marker"]
});

Describe alternatives you've considered
Ignore TS type checking.

Additional context
None.