Add official Xero server to servers readme

[Stanislav-Pankrashin]

Description

Server Details

• Server: Official Xero server
• Changes to: n/a - new server

Motivation and Context

Xero has developed an official MCP server.
Xero is a cloud accounting platform that provides trusted insights and functionality to millions of businesses around the world. Xero provides a comprehensive and robust API that is being leveraged within this MCP server. By providing an official MCP server, we can unlock the ability of our customers to interact with the Xero API using the MCP protocol

How Has This Been Tested?

This has been tested using the Claude desktop app. Future support for other clients will be present in future releases

Breaking Changes

N/A

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