Great job on the releasing the project; it definitely solves a need of being able to use declarative syntax for defining the relationships, and then customizing the layout which the regular layout generators can't do.

Project's Cargo.toml file says code is licensed under MIT license, but there's no license file in the repository, so Github doesn't show what the project is licensed under. Please add the license file so that people see it without having to dig through the code/configuration to determine that.