C is the native language of the plugin API. If you intend to use it, you don't need any special bindings.
There exists an official C++ wrapper around the C API. It can be found at https://github.com/mumble-voip/mumble-plugin-cpp.
Rust bindings are maintained independently from the main Mumble project. They can be found at https://crates.io/crates/mumble-sys.