Provide a stable setState method

[stefanhayden]

Hello. Thanks for all the hard work you put in here.

I was a bit surprised the setState function was not stable. In react when using useState that function is always stable. This repo, which does try and mirror that pattern, has made a different choice. I was looking at past conversations and I don't 100% understand why, but no worries.

I was wondering if you could also export a stable function like the one I have in this PR? I'm sure the static_setState is helpful to some but I don't see a reason to not also provide a more common stable function. I've been using it in my own project and I don't know of any downsides.

again, thanks for your hard work and I hope this kind of addition is considered.

[xplato]

Hey @stefanhayden, thanks for opening a PR!

The lack of stability in the setState function was an unfortunate mistake I made in some of the initial versions of useUndoable. It was, in fact, something I wanted to address in version 6, which I have a draft PR for now (although, I haven't been able to get back to it for some time).

Since v6 is a significant refactor, I would want to include these changes there (more precisely, I'll be replacing the definition of setState with the one you have here). I'll keep this PR open until I get those changes integrated, and give you an update at that time.

Thank you again for taking the time to improve the code here! You rock!