feat: add content resources

* Update index.md

Added a resource which i felt is important.

* Update index.md

fixing following guidelines

* Update index.md based on guide.

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

@@ -3,3 +3,5 @@
 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)
+- [@official@Official Website](https://www.rust-lang.org/)
+- [@opensource@Rust Book](https://edu.anarcho-copy.org/Programming%20Languages/Rust/rust-programming-language-steve-klabnik.pdf)