docs: improve documentation

[panz3r]

Description of Changes

This PR introduces several documentation and configuration improvements aimed at clarifying project structure, streamlining contribution processes, and enhancing issue and security management. The most significant updates include a comprehensive overhaul of the main README.md to better explain the monorepo structure and usage, new and improved issue and pull request templates, the addition of a dedicated security policy, and refinements to code ownership and dependency management.

Documentation and Project Structure:

• Major rewrite of README.md to clearly describe the monorepo structure, list all packages and examples, provide quick start and contribution instructions, and add a visual directory tree.
• Added project badges and improved package information in packages/google-signin/README.md. Also added contribution guidelines to the package README. [1] [2]
• Updated the Expo example README to reference the correct repository URL.
• Improved the core library README by removing redundant usage examples and clarifying the location of example integrations.

Repository Configuration and Templates:

• Refined .github/CODEOWNERS to clarify ownership patterns, add explicit owners for core, packages, examples, and CI/CD configuration, and ensure later matches take precedence.
• Enhanced .github/pull_request_template.md to include affected package checkboxes, a breaking changes section, improved testing instructions, and a Conventional Commits checklist item. [1] [2] [3]
• Overhauled issue templates for bugs and feature requests: added package selection dropdowns, improved reproduction steps, included a Code of Conduct agreement, and clarified environment/version fields. [1] [2] [3] [4] [5] [6]

Security and Contribution Process:

• Added a new SECURITY.md detailing how to report vulnerabilities, supported versions, response timelines, and in-scope areas for security issues.
• Updated CONTRIBUTING.md to reflect the use of pnpm -r lint instead of yarn lint for linting.

Dependency and Automation Management:

• Updated .github/dependabot.yml to include the packages/google-signin directory for dependency updates.

These changes collectively improve the developer experience, clarify contribution and support processes, and help maintain code and documentation quality across the project.

How to Test

1. CI Checks: Verify that all automated tests (Vitest) and build steps pass successfully on this PR.
2. Local Verification (Optional):
   • Run pnpm install (or equivalent).
   • Run the development server (pnpm dev or equivalent) for the library or examples to ensure Vite starts correctly.
   • Run a build (pnpm build or equivalent) to ensure it completes successfully.

Checklist

• My code follows the project's style guidelines
• I have added or updated tests to cover the changes
• I have updated relevant documentation
• All tests are passing locally
• CI checks are passing
• I have reviewed my own code and lock file changes
• I have checked for any potential security implications
• I have verified the changes work as expected

Notes for Reviewers