Vendor dependencies

Let's see how I like this workflow.

vendor/wasm-bindgen/guide/src/examples/webrtc_datachannel.md

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+# WebRTC DataChannel Example
+
+[View full source code][code] or [view the compiled example online][online]
+
+[online]: https://rustwasm.github.io/wasm-bindgen/exbuild/webrtc_datachannel/
+[code]: https://github.com/rustwasm/wasm-bindgen/tree/master/examples/webrtc_datachannel/
+
+This example creates 2 peer connections and 2 data channels in single browser tab.
+Send ping/pong between `peer1.dc` and `peer2.dc`.
+
+## `Cargo.toml`
+
+The `Cargo.toml` enables features necessary to use WebRTC DataChannel and its negotiation.
+
+```toml
+{{#include ../../../examples/webrtc_datachannel/Cargo.toml}}
+```
+
+## `src/lib.rs`
+
+The Rust code connects WebRTC data channel.
+
+```rust
+{{#include ../../../examples/webrtc_datachannel/src/lib.rs}}
+```