Comprehensive rewrite of React on Rails Pro README

This is a complete rewrite of the React on Rails Pro README.md to address
all identified issues and better serve as the entry point for a commercial
product.

Key improvements:

### Structure & Content
- Added comprehensive table of contents for easy navigation
- Clear explanation of what React on Rails Pro is and its relationship to open source
- Prominent licensing information (free for non-commercial, paid for production)
- Added "Why Use Pro?" section with real-world performance case study (Popmenu)
- Comparison table showing Pro vs. Open Source features
- Complete FAQ section addressing licensing, technical, and getting started questions

### Installation & Getting Started
- Quick start guide (5 minutes from zero to running)
- Clear prerequisites and compatibility matrix
- Instructions for installing from public monorepo (no more private GitHub packages confusion)
- Step-by-step verification instructions

### Features
- Expanded feature descriptions with code examples
- Benefits listed for each feature
- Links to detailed documentation
- Practical examples showing actual usage

### Documentation
- Organized docs into logical categories (Installation, Features, API)
- Brief descriptions of what each doc contains
- Clear upgrade guidance pointing to CHANGELOG

### Support & Contact
- Multiple ways to get help (email, documentation)
- Professional services information
- About ShakaCode section

### Badges & Metadata
- Removed fake CircleCI badge
- Added real GitHub Actions badges for Pro workflows
- Added commercial license badge
- All badges link to actual workflows

### Examples
- Explained the Pro dummy app and how to run it
- Listed features demonstrated in the example
- Linked to real-world production example (Popmenu)

### Licensing
- Clear explanation that it's free for non-commercial use
- Instructions to get FREE 3-month license in 30 seconds
- Link to comprehensive LICENSE_SETUP.md
- Explained difference between free and commercial licenses

This README now properly positions React on Rails Pro as a commercial
product while making it easy for developers to evaluate and get started.

Fixes all 20+ issues documented in react_on_rails_pro_readme_issues.md.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: justin808