feat: basic ffi server to support other languages (#34)

* wip

* wip

* wip

* wip

not a fan of the way I do handles ..

* errors and async semantic

* fix example

webrtc-sys/src/video_frame.rs

@@ -1,3 +1,5 @@
+use crate::impl_thread_safety;
+
 #[cxx::bridge(namespace = "livekit")]
 pub mod ffi {
     #[derive(Debug)]
@@ -30,3 +32,5 @@ pub mod ffi {
         fn _unique_video_frame() -> UniquePtr<VideoFrame>; // Ignore
     }
 }
+
+impl_thread_safety!(ffi::VideoFrame, Send + Sync);