C++ APPI

[emassey0135]

The CXX crate seems very easy to use, and requires no unsafe Rust. It also says it does no memory allocation or copying by default, so it would be interesting to compare a C++ API created using this to the C API for performance. This would also let C++ applications free structures with the standard "delete" instead of calling custom functions, throw C++ exceptions instead of requiring you to check for errors constantly and get the string with whisprs_get_last_error, have features like namespaces and classes that can make names less verbose, and maybe implement things like optional parameters and the error enum in a higher level way, by using things like function overloading and custom classes.