Add crates.io badges and documentation improvements

[RAprogramm]

Add additional badges and improve README with crates.io metrics.

Objectives

• Add crates.io downloads badge
• Add docs.rs build status badge
• Add lib.rs badge
• Improve README presentation

New Badges

Crates.io Downloads

[![Downloads](https://img.shields.io/crates/d/cstring-array.svg)](https://crates.io/crates/cstring-array)

Docs.rs Build Status

[![Docs.rs](https://docs.rs/cstring-array/badge.svg)](https://docs.rs/cstring-array)

(Already have this one)

Lib.rs

[![Lib.rs](https://img.shields.io/badge/lib.rs-cstring--array-blue)](https://lib.rs/crates/cstring-array)

Categories Badge

[![Category](https://img.shields.io/crates/c/cstring-array)](https://crates.io/categories)

README Improvements

• Reorganize badges in logical groups
• Add quick navigation table of contents
• Improve feature highlights
• Add comparison with alternatives
• Add FAQ section

Implementation

• Test all badge URLs work correctly
• Add badges to README.md
• Organize in clean layout
• Ensure mobile-friendly display
• Verify after publishing to crates.io

Benefits

• Show project popularity (downloads)
• Build confidence with metrics
• Professional appearance
• Better discoverability
• Standard for popular crates