Add an example of webrtc-direct (#868)

Co-authored-by: Vasco Santos <vasco.santos@moxy.studio>

examples/webrtc-direct/README.md

@@ -0,0 +1,33 @@
+### Webrtc-direct example
+
+An example that uses [js-libp2p-webrtc-direct](https://github.com/libp2p/js-libp2p-webrtc-direct) for connecting
+nodejs libp2p and browser libp2p clients. To run the example:
+
+## 0. Run a nodejs libp2p listener
+
+When in the root folder of this example, type `node listener.js` in terminal. You should see an address that listens for
+incoming connections. Below is just an example of such address. In your case the suffix hash (`peerId`) will be different.
+
+```bash
+$ node listener.js 
+Listening on:
+/ip4/127.0.0.1/tcp/9090/http/p2p-webrtc-direct/p2p/QmUKQCzEUhhhobcNSrXU5uzxTqbvF1BjMCGNGZzZU14Kgd
+```
+
+## 1. Prepare a browser libp2p dialer
+Confirm that the above address is the same as the field `list` in `public/dialer.js`:
+```js
+    peerDiscovery: {
+      [Bootstrap.tag]: {
+        enabled: true,
+        // paste the address into `list`
+        list: ['/ip4/127.0.0.1/tcp/9090/http/p2p-webrtc-direct/p2p/QmUKQCzEUhhhobcNSrXU5uzxTqbvF1BjMCGNGZzZU14Kgd']
+      }
+    }
+```
+
+## 2. Run a browser libp2p dialer
+When in the root folder of this example, type `npm run dev` in terminal. You should see an address where you can browse
+the running client. Open this address in your browser. In console
+logs you should see logs about successful connection with the node client. In the output of node client you should see
+a log message about successful connection as well.