Write comprehensive README.md documentation

[Copilot]

This PR adds comprehensive documentation to the Navix Browser project, transforming the minimal 2-line README into a detailed guide that covers all aspects of the project.

What's Changed

📚 Comprehensive Documentation

The new README.md includes:

• Detailed project overview explaining Navix as a modern Java-based browser built on JCEF
• Complete features list covering core browsing, privacy & security, themes, configuration, and developer features
• Installation instructions with both pre-built releases and build-from-source options
• Configuration guide including Google Safe Browsing API setup
• Usage documentation for basic browsing, privacy features, downloads, and themes
• Development guide with project structure, key components, and contribution guidelines
• Troubleshooting section addressing common build and runtime issues

🔧 Developer Experience Improvements

• Added SECRETS.java.template file to help developers set up Google Safe Browsing API keys securely
• Detailed build instructions with Maven commands
• Project structure documentation for new contributors
• Clear dependency information and requirements

🛡️ Security Considerations

• Proper handling of sensitive API keys with template file approach
• Clear instructions on keeping API keys secure and out of version control
• The actual SECRETS.java file remains properly excluded via .gitignore

Key Features Documented

The documentation highlights Navix Browser's impressive feature set:

• Privacy-focused: Built-in ad blocking, tracker protection, and Google Safe Browsing integration
• Customizable: Multiple themes (Modern, System, Cross-Platform) with dark mode support
• Developer-friendly: DevTools integration, debug port access, and extensive configuration options
• Modern UI: Tabbed browsing with download manager and customizable new tab page

This documentation makes the project much more accessible to new users and contributors, providing clear guidance for installation, configuration, and development.

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💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.