Arabic translation of The Rust Programming Language

Hi! I've completed a full Arabic translation of The Rust Programming Language, following the book's source structure 1:1 (same chapter files, same SUMMARY.md ordering, same listings).

Repository: https://github.com/Khaled-Ghallab/book-rust-ar

• Builds cleanly with mdbook build, no broken links/references.
• Dual-licensed MIT/Apache-2.0, matching the original.
• RTL layout configured in book.toml.

Happy to keep improving it based on feedback. Please let me know if there's anything needed before it can be added to the Translations list in appendix-06-translation.md.