Complete `onConnected` with error if connection fails to open (dart-lang/sse#42)

* Complete `onConnected` with error if connection fails to open

This prevents `onConnected` from hanging indefinitely if the `SseClient`
immediately fails to open.

Fixes https://github.com/dart-lang/sse/issues/41.

* Recompile the test app

* Add changelog entry and update version
4 files changed
tree: 55a40baddb0f1475a65cd4d7ef5029fe2caac2ca
  1. pkgs/