feat: update to dart 3

[gnudles]

No description provided.

[gnudles]

Hi, thanks.
Can you update the version number in the pubspec, to 1.0.0, and also add some notes in the changelog?
Another thing.... if we move to version 3, maybe we no longer want null-safe to be optional, but mandatory? so the version check should be removed. But if we keep it optional, then all the "reorder**" new strings should be included by condition

[lvxduck]

I think that we should remove the version check because Dart 3 requires sound null safety. If anyone needs unsound null safety, they can use the lower version.

[gnudles]

published the changes