fr(google-maps): add forRoot() for global initializing

#### Feature Description

like many modules already use it, it would be nice if you could initialize the Google Map with the method `forRoot()` in `app.module.ts` with given parameters.

#### Use Case

initialize with parameters like:

- apiKey (link apiKey from environment.ts)
- language
- region
- styles (set global styles for map and marker)

These are the first ones I thought of. I'm sure there are many [more](https://angular-maps.com/api-docs/agm-core/interfaces/lazymapsapiloaderconfigliteral#info).

Start by reviewing the existing Google Maps module usage in app.module.ts and the configuration source in environment.ts. Compare the requested apiKey, language, region, and styles options with the linked AGM API documentation. Done means a forRoot() initialization path accepts the required global parameters and supports the described use case.

Written by the indexing model from the issue text.