creata a short wiki for WebRTC when users click on "What do these policies mean?"

[kjozwiak]

Description

When a user clicks on What do these policies mean? under about:preferences#security for the WebRTC feature, it will take them to the following header file:

• https://cs.chromium.org/chromium/src/content/public/common/webrtc_ip_handling_policy.h

Most average and some power users won't understand the above header file which will lead to confusion. We should create a short summary in a wiki that explains what the feature does and include the above link for more advanced users.

Steps to Reproduce

1. open brave and open about:preferences#security
2. click on the What do these policies mean? link

[btlechowski]

Verified on Ubuntu 17.10 x64

• 0.22.703 903b8d0
• libchromiumcontent 66.0.3359.139
• muon: 6.0.8

Verified on Windows x64

• 0.22.703 903b8d0
• libchromiumcontent 66.0.3359.139
• muon: 6.0.8

Verified with macOS 10.12.6 using

• 0.22.703 903b8d0
• muon 6.0.8
• libchromiumcontent 66.0.3359.139