Use web_socket_channel in the README.

Closes dart-lang/json_rpc_2#8

R=tjblasi@google.com

Review URL: https://codereview.chromium.org//1780583002 .
1 file changed
tree: f1a8d6356b1c83dd08fb6f4244b2848889f3e2b2
  1. pkgs/