Basically translated Ryuji (originally written in Typescript) to Rust, to allow usage in Rust, and also hopefully for increased speed. We'll see...
Translating wasn't very easy, since Rust is a lot stricter. It was pretty fun though.
See an example in example directory, or in the tests in src/lib.rs. Another example of Ryuji syntax (which uses the Typescript library not the Rust library) can be found at hedgeblog.
The library documentation is probably on docs.rs, and the templating language docs is here.