docs: Add y-cli to the list of clients

[luohy15]

Add y-cli to the list of MCP clients

Motivation and Context

This PR adds y-cli, a new CLI chat application with MCP support, to our list of MCP-compatible clients.
As a terminal fan, I hope to have MCP capabilities directly in the terminal.

How Has This Been Tested?

see demo in asciinema

Breaking Changes

None. This is a documentation-only change that adds a new client to the list.

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 Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context