Add examples/ortc README

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Relates to #379

Author: Sean-Der

examples/ortc/README.md

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+# ortc
+ortc demonstrates Pion WebRTC's [ORTC](https://ortc.org/) capabilities. Instead of using the Session Description Protocol
+to configure and communicate ORTC provides APIs. Users then can implement signaling with whatever protocol they wish.
+ORTC can then be used to implement WebRTC. A ORTC implementation can parse/emit Session Description and act as a WebRTC
+implementation.
+
+In this example we have defined a simple JSON based signaling protocol.
+
+## Instructions
+### Download ortc
+```
+export GO111MODULE=on
+go get github.com/pion/webrtc/v3/examples/ortc
+```
+
+### Run first client as offerer
+`ortc -offer` this will emit a base64 message. Copy this message to your clipboard.
+
+## Run the second client as answerer
+Run the second client. This should be launched with the message you copied in the previous step as stdin.
+
+`echo BASE64_MESSAGE_YOU_COPIED | ortc`
+
+### Enjoy
+If everything worked you will see `Data channel 'Foo'-'' open.` in each terminal.
+
+Each client will send random messages every 5 seconds that will appear in the terminal
+
+Congrats, you have used Pion WebRTC! Now start building something cool