remove C++ & CMake?

[Be-ing]

Hi, I found your repository from CXX-Qt's dependency graph on GitHub. It looks like the only C++ in your repository is the tiny main.cpp file. As of CXX-Qt 0.5, you don't need that anymore. You can now register QML types and QRC resources from build.rs and have your main function in Rust without any C++ boilerplate. Take a look at https://github.com/KDAB/cxx-qt/tree/main/examples/cargo_without_cmake