Documentation update for JsonEncoder and JsonDecoder class
Documentation update for JsonEncoder and JsonDecoder class

Added example codes for classes: JsonEncoder and JsonDecoder.
Added example codes for functions: jsonEncode and jsonDecode.

Closes https://github.com/dart-lang/sdk/pull/47430
https://github.com/dart-lang/sdk/pull/47430

GitOrigin-RevId: c3015fb09cd72a3441b338a3266886ed262b03b3
Change-Id: I0a58c95e43421efca34ccda9d776454fddfbdb9c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/216200
Reviewed-by: Lasse R.H. Nielsen <80295e4ef244a07779f93eaa95d582bad8e316a5@google.com>
Commit-Queue: Lasse R.H. Nielsen <80295e4ef244a07779f93eaa95d582bad8e316a5@google.com>

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