README: Add Apache Pinot Official MCP Server

[KKcorps]

Description

Add official Apache Pinot MCP server (https://github.com/startreedata/mcp-pinot) on Official integrations section.

Server Details

• Server: Apache Pinot MCP Server
• Changes to: Adding a new server entry to the README.md

Motivation and Context

This MCP server equips AI Agents with tools to interact with Apache Pinot through a standardized and extensible interface.

How Has This Been Tested?

Integration with the server was tested using Claude Desktop by our devs. All Authentication modes were vetted along with all the exposed tools

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