Add resource link (#6419)

* Update index.md

* Update index.md

src/data/roadmaps/rust/content/100-introduction/index.md

@@ -2,3 +2,4 @@
 
 Rust is a modern system programming language focused on performance, safety, and concurrency. It accomplishes these goals without having a garbage collector, making it a useful language for a number of use cases other languages aren’t good at. Its syntax is similar to C++, but Rust offers better memory safety while maintaining high performance.
 
+- [@official@Rust by Example](https://doc.rust-lang.org/stable/rust-by-example/index.html)