Handle GitHub API rate limit errors gracefully and add docs

[Ashish04500]

Summary

This PR fixes the GitHub API rate limit issue and improves the documentation.

Changes

• Added proper error handling for rate limit responses (403 Forbidden with rate limit exceeded message).
• Updated README.md with a clear note about GitHub’s 10 unauthenticated search requests per minute limit.
• Suggested using a GitHub personal access token (PAT) for frequent use to avoid hitting the limit.

Why

Currently, the CLI fails silently or shows confusing errors when the rate limit is exceeded.
This update provides better UX and guidance to the user.

Test

• Ran node ./bin/good-first-issue.js nodejs/node without authentication and verified that the rate limit message appears.
• Confirmed functionality remains unchanged when within rate limits.

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Closes #<issue_number_if_any>

[Ashish04500]

Hi! This PR handles the GitHub API rate limit error gracefully and updates the README with instructions for using --auth. Let me know if any changes are needed!