Add Mapbox MCP Server to server list

[angelanavarro]

Description

This PR adds the Mapbox MCP server to the official integrations list

Server Details

• Server: https://github.com/mapbox/mcp-server
• Changes to: README.md

Motivation and Context

Mapbox APIs give agents the ability to become aware of geographic context and enable AI tools to use Mapbox maps.

How Has This Been Tested?

The Mapbox MCP server has been tested with Claude desktop, LangGraph and smolagents.

Breaking Changes

None

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [X] Documentation update

Checklist

• [X] I have read the MCP Protocol Documentation
• [X] My changes follows MCP security best practices
• [X] I have updated the server's README accordingly
• [X] I have tested this with an LLM client
• [X] My code follows the repository's style guidelines
• [X] New and existing tests pass locally
• [X] I have added appropriate error handling
• [X] I have documented all environment variables and configuration options

Additional context