Summary: GitHub Copilot adds usage limits and purchase options

Why It Matters: This change tells users about how GitHub Copilot works during busy times. It also explains how some users cannot buy more requests.

What Changed:

• Add information about GitHub Copilot response times during high usage
• Add information about rate limiting for GitHub Copilot requests
• Add a note that users who subscribe to Pro or Pro+ through GitHub Mobile cannot buy more premium requests