feat: Migrate and modernize React basic map with marker

[willum070]

Description

This PR introduces the rgm-basic-map sample to the repository, migrating the foundational React map patterns and adding marker functionality for completeness. It serves as the baseline example for developers looking to integrate the Google Maps JavaScript API natively within a React application using the community-standard @vis.gl/react-google-maps library.

Key Changes

• Sample Migration: Migrated rgm-basic-map from js-samples.
• Configuration Updates: Updated package names, HTML meta titles, and region tags (maps_rgm_basic_map) to accurately reflect the new sample structure.
• Code Cleanup: Formatted the codebase with Prettier and removed unused CSS (gmp-map), as the @vis.gl wrapper programmatically mounts a standard <div> that inherits from the root container.
• Documentation Expansion: Authored a comprehensive README.md to establish best practices for React developers, explicitly covering:
  • Using <APIProvider> for optimal script loading and React Context management.
  • Demonstrating declarative, "uncontrolled" map state using <Map defaultCenter={...}>.
  • The requirement of passing a mapId to enable Cloud-based styling and Advanced Markers.
  • Rendering modern <AdvancedMarker> components instead of legacy google.maps.Marker classes.

Testing

• Verified all TypeScript and ESLint checks pass (npm run build).
• Verified the sample successfully runs locally (npm start) and correctly renders the map and Advanced Marker on the screen.

[snippet-bot]

Here is the summary of changes.

You are about to add 2 region tags.

• samples/rgm-basic-map/index.html:7, tag maps_rgm_basic_map
• samples/rgm-basic-map/src/app.tsx:7, tag maps_rgm_basic_map

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