Editor image dialog: option to sync the width and height of the image and also option to override the sync

Description of the need

Almost always someone wants to keep the width and height synced so as not to distort the image. It would be nice to keep them synced automatically. But there may be times that someone wants to stretch or squeeze an image so there should also be an option to override.

There's also this related issue: https://github.com/backdrop/backdrop-issues/issues/3599

Proposed solution

There is a contrib module that gets most of the way: https://github.com/backdrop-contrib/editorimgdimensionsync. Just need an option to override this sync in case someone wants to not keep the ratio.

Alternatives that have been considered

There is the alternative but hard to discover. This is a simple feature that would be used by almost everyone most of the time.