Improve documentation of integers endianness.
Improve documentation of integers endianness.

Added to the documentation that integers should be of the same endianness of the host.

- I have lost 2 hours to discover that `asUint32List` requires the same endianness of `Endian.host`.

Closes https://github.com/dart-lang/sdk/pull/47980
https://github.com/dart-lang/sdk/pull/47980

GitOrigin-RevId: 1a1728602735434efd3e505d76e4f45b8161ea14
Change-Id: Id8a1fd8c5c4dced141881a1ce64577fdcbb8b62e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/225080
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