add+ vietnamese translate

Author: tuanemdev

src/appendix-06-translation.md

@@ -26,3 +26,4 @@ For resources in languages other than English. Most are still in progress; see
 - [हिंदी](https://github.com/venkatarun95/rust-book-hindi)
 - [ไทย](https://github.com/rust-lang-th/book-th)
 - [Danske](https://github.com/DanKHansen/book-dk)
+- [Tiếng Việt](https://github.com/tuanemdev/rust-book-vn)