Add official Todoist MCP server to README

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Description

Todoist's official MCP server was not on the list yet.

Server Details

• Server: https://github.com/doist/todoist-ai

Motivation and Context

Todoist's official MCP server was not on the list yet.

How Has This Been Tested?

The MCP server is always tested manually in Claude Desktop before any change to the tools' implementation.

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

N/A