Feature Request: Add Copilot Review Support to GitHub MCP Server

Description

As a user of the GitHub MCP Server, I would like to be able to request a GitHub Copilot review for a pull request through the MCP API, similar to how we can request reviews from human reviewers.

Current Behavior

Currently, the MCP Server supports requesting human reviewers for pull requests, but there's no mechanism to request GitHub Copilot reviews programmatically.

Desired Behavior

Add a method to request GitHub Copilot review for pull requests. This could be implemented as:

1. New API endpoint: request_copilot_review function
2. Enhanced existing method: Allow request_pull_request_review to accept "copilot" as a reviewer
3. Hybrid approach: Add a flag to enable Copilot review when creating/updating pull requests

Use Case

When creating or managing PRs programmatically through the MCP, developers should be able to leverage GitHub Copilot's code review capabilities without needing to manually enable it through the GitHub UI.