Deprecate this library

[ErikHellman]

This library is not really needed anymore. The custom test runner only works for Firefox and Chrome on Linux. The eslint configuration can be replaced with a standard one instead.

[samdutton]

Reasoning makes sense, though you should probably check with the contributors. (I've never worked on this.)

[ErikHellman]

Ping @fippo and @KaptenJansson.

[fippo]

@KaptenJansson is probably still dealing with :baby:

most of this depends a decision how tests are done. The buildDriver variant herein uses a shared instance which is way faster than starting the browser a dozen times like the samples would do.

Can't speak for the https://github.com/webrtc/testrtc dependency though.