Mention `ready` in the docs for `connect` (dart-lang/web_socket_channel#287)

Closes dart-lang/web_socket_channel#280

There can be confusion when there are errors creating the channel
because the only wait to catch them is to include an `await
channel.ready` in the try block. Mention that `ready` can complete as an
error in the case of connection failure.
3 files changed
tree: da329fa859dc7b256f6ce4cd1840de19fdf68819
  1. pkgs/