Add comprehensive README.md with project overview, build instructions, and customizations

[Copilot]

This PR addresses the missing documentation by adding a comprehensive README.md file that provides essential information for developers and users of the ProxyLib project.

What's Added

The new README.md includes:

Project Overview

• Clear description of ProxyLib as a Windows DLL proxy library with reflective loading capabilities
• Key features including transparent proxying, cross-architecture support, and runtime code generation
• Work-in-progress disclaimer noting the project's active development status

Architecture Support Matrix

• ✅ x86 (32-bit): Fully supported
• ✅ x64 (64-bit): Fully supported
• ❌ ARM/ARM64: Not currently supported (as specified in the requirements)

Complete Build Instructions

• Prerequisites and required tools (CMake, Python, MSVC/MinGW/Clang)
• Step-by-step build process for different environments
• Multiple configuration examples for debug and production builds

Customization Documentation

• Comprehensive table of CMake configuration options
• Examples for targeting different system DLLs
• Runtime configuration through callback system
• Advanced PE manipulation features

Usage Examples

• Basic integration with C callback functions
• Advanced usage with C++ lambda callbacks
• Project structure overview

Troubleshooting Guide

• Common build issues and solutions
• Debug configuration recommendations
• Platform-specific considerations

Current Limitations Documented

The README clearly states the current limitations as requested:

• Windows-only support (primary target platform)
• No ARM/ARM64 architecture support in current state
• User-mode DLL restrictions
• Compatibility considerations with protected applications

This documentation will help new contributors understand the project's capabilities, build requirements, and current development status while providing clear guidance for customization and usage.

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