Update documentation and add Rewardful plugin to external plugins list

[iloveitaly]

Summary

This PR updates documentation across multiple README files, improves the contributing guide, and adds a new community plugin to the external plugins registry.

Key Changes

• Documentation Updates: Updated plugin version numbers across README files to reflect latest releases (e.g., @analytics/core 0.12.9 → 0.13.2, @analytics/google-analytics 1.0.7 → 1.1.0)
• API Documentation: Clarified that the callback parameter in the disable() method is optional by updating the documentation format from callback to [callback] (optional)
• Table of Contents: Added emoji to "Install" section header and added new "Support" section to the table of contents
• Contributing Guide: Added comprehensive documentation for the npm run docs command, explaining when and how to regenerate auto-generated content in README files
• External Plugins: Added Rewardful plugin to the community plugins list in external-plugins.json
• Gitignore: Added package-lock.json to .gitignore

Notable Details

• The plugin version updates appear to be auto-generated content reflecting the current state of published packages
• Documentation changes maintain consistency across three README files (root, packages/analytics-core, and packages/analytics)
• The contributing guide now explicitly instructs contributors to run npm run docs when modifying external-plugins.json or API documentation

https://claude.ai/code/session_014g18gLxH3CAbPWHBVcyf4W