make webrtc-rs optional feature

src/lib.rs

@@ -59,7 +59,12 @@ pub mod fingerprint;
 pub use flexi_logger;
 pub mod stream;
 pub mod websocket;
+#[cfg(feature = "webrtc")]
 pub mod webrtc;
+#[cfg(not(feature = "webrtc"))]
+pub mod webrtc_dummy;
+#[cfg(not(feature = "webrtc"))]
+pub use webrtc_dummy as webrtc;
 #[cfg(any(target_os = "android", target_os = "ios"))]
 pub use rustls_platform_verifier;
 pub use stream::Stream;