Don't need to prompt to save if the file hasn't changed

[psheill]

unneeded dialog

[peterjthomson]

Good point. This is a multi year issue from the MarkTree to do with the app thinking that any differences between the output of it's read, edit, write lifecycle from the file on disk are intentions changes. Basically re-applying linting to every file whether you want it or not. I think I have a partial solution and have merge here:
https://github.com/peterjthomson/marktext/blob/master/docs/features/light-touch.md

Once I merge the other features from the current sprint. I'll tag a release and maybe try again?