Add code of conduct to WebRTC repo

CODE_OF_CONDUCT.md

+# Contributors Code of Conduct
+
+Google and the WebRTC team are committed to preserving and fostering a diverse, welcoming and open
+community. The WebRTC project is open to contributors from all  walks of life and should be a
+harassment-free experience for everyone, regardless of age, body size, disability, ethnicity, gender
+identity and expression, level of experience, nationality, personal appearance, race, religion, or
+sexual identity and orientation.
+
+## Scope
+This Code of Conduct applies to our repos and organizations, mailing lists, blog content, and any
+other WebRTC-supported communication group, as well as any private communication initiated in the
+context of these spaces.
+
+## Standards
+Examples of behavior that contributes to creating a positive environment include:
+
+* Using welcoming and inclusive language
+* Being respectful of differing viewpoints and experiences
+* Gracefully accepting constructive criticism
+* Focusing on what is best for the community
+* Showing empathy towards other community members
+
+Examples of unacceptable behavior by participants include:
+
+* The use of sexualized language or imagery and unwelcome sexual attention or advances
+* Trolling, insulting/derogatory comments, and personal or political attacks
+* Public or private harassment
+* Publishing others' private information, such as a physical or electronic address, without explicit
+permission
+* Other conduct which could reasonably be considered inappropriate in a professional setting
+
+## Responsibilities
+
+You are empowered to politely engage when you feel that you or others are disrespected. The person
+making you feel uncomfortable may not be aware of what they are doing - politely bringing their
+behavior to their attention is encouraged.
+
+If you are uncomfortable speaking up, or feel that your concerns are not being duly considered, you
+can email community@webrtc.org to request involvement from a community manager. All concerns shared
+with community managers will be kept confidential. While all reports will be taken seriously, the
+WebRTC community managers may not act on complaints that they feel are not violations of this code
+of conduct.
+
+## Enforcement
+
+Consequences for failing to comply with this policy may include, at the sole discretion of the
+WebRTC community managers:
+
+* a request for an apology;
+* a private or public warning or reprimand;
+* a temporary ban from the mailing list, blog, WebRTC repository or organization, or other
+WebRTC-supported communication group, including loss of committer status;
+* a permanent ban from any of the above, or from all current and future WebRTC-supported or
+Google-supported communities, including loss of committer status.
+
+Participants warned to stop any harassing behavior are expected to comply immediately; failure to do
+so will result in an escalation of consequences.
+
+The decisions of the WebRTC community managers may be appealed via community-appeals@webrtc.org.
+
+## Acknowledgements
+
+This Code of Conduct is based on Contributor Covenant, version 1.4,
+available [here](http://contributor-covenant.org/version/1/4) and [Chromium](https://chromium.googlesource.com/chromium/src/+/master/CODE_OF_CONDUCT.md)
+
+## License
+
+This Code of Conduct is available for reuse under the Creative Commons Zero (CC0) license.