feat: add publishing & audio to ffi (#46)

- Divide FFI protocol into multiple files
- Audio support
- AV Streams/Sources
- Create tracks
- Use Dashmap to store handles
- Add a capture test
     - Ignored by GHA atm

livekit-webrtc/src/audio_source.rs

@@ -18,7 +18,7 @@ pub mod native {
     }
 
     impl NativeAudioSource {
-        pub fn capture_frame(&self, frame: AudioFrame) {
+        pub fn capture_frame(&self, frame: &AudioFrame) {
             self.handle.capture_frame(frame)
         }
     }