Fix error thrown when inserting keys (dart-lang/yaml_edit#80)

* Check for key order only when one key is present

* Update tests to match latest fix

> Add tests for key order

* Add golden tests for fix

* Skip random test until issue dart-lang/yaml_edit#85 is fixed

* Update changelog
10 files changed
tree: a6052e4bb2d2b682e46ef041ddd9438d923ae5ca
  1. pkgs/