Rust 1.48
One of the things that made me so excited about Rust when I first used it was the capabilities of the Rustdoc system. The built in examples that are also unit tests, the ease of just using markdown... and now the linking is even simpler. It’s one of my favorite things about the language, and I think is why so many crates have such good documentation, because it’s easy to do. (and it’s tested and validated so you know it’s right!)