Add Nango MCP Server (Readme server's list)

[rguldener]

Description

Add Nango MCP server to the list in the Readme

Motivation and Context

Allow users to discover the built-in MCP server of Nango for 500+ APIs.

How Has This Been Tested?

We have tested Nango's MCP server with Cursor, Claude (Desktop & Code), and a few others.

Breaking Changes

No. Just a docs update.

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)
• Documentation update

Checklist

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

Additional context