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

webrtc-sys/src/video_frame.rs

@@ -22,8 +22,8 @@ pub mod ffi {
 
         type VideoFrame;
 
-        fn width(self: &VideoFrame) -> i32;
-        fn height(self: &VideoFrame) -> i32;
+        fn width(self: &VideoFrame) -> u32;
+        fn height(self: &VideoFrame) -> u32;
         fn size(self: &VideoFrame) -> u32;
         fn id(self: &VideoFrame) -> u16;
         fn timestamp_us(self: &VideoFrame) -> i64;