Add githubapi.py module documentation to README

[Copilot]

The README documented individual scripts but not the githubapi.py module that all scripts depend on.

Added comprehensive documentation section covering:

• Module overview: Authentication, pagination, rate limiting, and GHAS alert access
• GitHub class: Initialization patterns for github.com, GHES, custom CA bundles, and TLS options
• Core methods: query(), list_code_scanning_alerts(), list_secret_scanning_alerts(), list_dependabot_alerts()
• Utility functions: parse_date() with relative (7d) and absolute date formats
• Error handling: Automatic rate limit backoff and connection error behavior

Example usage:

from githubapi import GitHub, parse_date

gh = GitHub()
since = parse_date("30d")

for alert in gh.list_secret_scanning_alerts(
    name="my-org",
    scope="org", 
    state="open",
    since=since
):
    print(f"{alert['secret_type']} in {alert['repository']['full_name']}")

Positioned between Requirements and Usage sections for logical flow from setup → library → scripts.

Original prompt

Please add documentation to README.md on how the githubapi.py works

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

[Copilot]

Pull Request Overview

This PR adds comprehensive documentation for the githubapi.py module to the README. The module is a lightweight GitHub API client that all scripts in the repository depend on, and was previously undocumented.

Key changes:

• Added new "The githubapi.py Module" section with detailed API documentation
• Reorganized README structure by renaming "Usage" to "Scripts usage" for clarity
• Documented the GitHub class, including initialization patterns, core methods, and utility functions
• Provided complete usage examples showing how to use the module programmatically

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.