Add methods to Result. Bump version to 2.0 and remove deprecated features.

lib/src/result/capture_transformer.dart

Index: lib/src/result/capture_transformer.dart
diff --git a/lib/src/result/capture_transformer.dart b/lib/src/result/capture_transformer.dart
index 6b1bbf239cd24e9efb8de5fa0a68015412f9583a..22534e5a42c0a492feabe594b8c92b192e8cee33 100644
--- a/lib/src/result/capture_transformer.dart
+++ b/lib/src/result/capture_transformer.dart
@@ -10,8 +10,7 @@ import 'capture_sink.dart';
 /// A stream transformer that captures a stream of events into [Result]s.
 ///
 /// The result of the transformation is a stream of [Result] values and no
-/// error events. This is the transformer used by [captureStream].
-@Deprecated("Will be removed in async 2.0.0.")
+/// error events. Exposed by [Result.captureStream].
 class CaptureStreamTransformer<T> implements StreamTransformer<T, Result<T>> {
   const CaptureStreamTransformer();