[Documentation] Add system dependencies and installation requirements

[PhiAlex-baiye]

Problem

The current README doesn't mention the requirement for Python development headers, causing compilation failures on fresh systems.

Error Message

致命错误：Python.h：没有那个文件或目录
    2 | #include <Python.h>
      |          ^~~~~~~~~~
编译中断。

Impact

• New users cannot compile the project without additional system packages
• moon run and moon test both fail immediately
• No clear guidance on what dependencies are needed

Solution

Add a "System Requirements" section to README with installation commands for different distributions:

System Requirements

Fedora/RHEL/CentOS:

sudo dnf install python3-devel

Debian/Ubuntu:

sudo apt-get install python3-dev

Arch Linux:

sudo pacman -S python

macOS:

# Usually included with Xcode Command Line Tools
xcode-select --install

# Or via Homebrew
brew install python

Environment

• OS: Fedora 42 (Linux 6.15.8-200.fc42.x86_64)
• Python: 3.13.5
• Error occurs: During compilation of C extensions

Additional Information

This requirement exists because:

1. The project uses Python C API through Kaida-Amethyst/python dependency
2. C compilation requires Python development headers (Python.h)
3. Most Linux distributions separate runtime packages from development packages

Suggested README Section

## System Requirements

### Python Development Headers

This project requires Python development headers for C extension compilation.

**Linux (Fedora/RHEL/CentOS):**
```bash
sudo dnf install python3-devel

Linux (Debian/Ubuntu):

sudo apt-get install python3-dev

Linux (Arch):

sudo pacman -S python

macOS:

xcode-select --install

Verification:
After installation, verify the headers are available:

python3-config --includes
# Should output something like: -I/usr/include/python3.13

## Related Issues

This documentation fix will prevent the compilation issues described in other related bugs.