Not working on WebGL?

I followed this guide:
https://github.com/bengreenier/webrtc-unity-plugin

downloaded the example and try to build with webgl the demo scene:
I get lot of errors

To Reproduce
Install unity 2019.4.11
follow the guide
try to build for webgl

Expected behavior
I can compile

Environment (please complete the following information):

OS: Windows
Unity Version [e.g. 2019.4.11f]
Is normal or I am doing something wrong?

Start with the linked guide and reproduce the WebGL build of the demo scene using Unity 2019.4.11 on Windows. Record the build errors and compare them with the example setup; the issue is resolved when the demo compiles for WebGL or the incompatibility is clearly identified.

Written by the indexing model from the issue text.