Documentation update for Stream and StreamSubscription
Documentation update for Stream and StreamSubscription

Stream method examples added
StreamSubscription example added.
Minor grammar corrections.

Closes https://github.com/dart-lang/sdk/pull/47988
https://github.com/dart-lang/sdk/pull/47988

GitOrigin-RevId: efcad442dee45cc8e7f5e20bf459e1102dd1d2a9
Change-Id: Ie291cb9c7c7b3d9ceef079642e53ec4c5a6809e8
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/225160
Reviewed-by: Lasse Nielsen <80295e4ef244a07779f93eaa95d582bad8e316a5@google.com>
Commit-Queue: Lasse Nielsen <80295e4ef244a07779f93eaa95d582bad8e316a5@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk