feat: add import of store state json to devtools middleware

[jose-vale]

Currently it is possible to export the state of the store in redux devtools, but it is not possible to import, this PR adds this functionality.

devtools.mov

[codesandbox-ci]

This pull request is automatically built and testable in CodeSandbox.

To see build info of the built libraries, click here or the icon next to each commit SHA.

Latest deployment of this branch, based on commit 8807cae:

Sandbox	Source
React	Configuration
React Typescript	Configuration

[dai-shi]

Wow, this looks nice. Where can I learn about IMPORT_STATE?
https://github.com/zalmoxisus/redux-devtools-extension/blob/master/docs/API/Methods.md doesn't seem to have enough spec.

I'm pretty sure this won't break anything, but could anyone review the code?
Also, we would like to apply the same technique to jotai and valtio. (any volunteers? maybe I should create an issue in each repo.)

[jose-vale]

There doesn't seem to be any information in the docs that I could find. When looking into this, I was able to find a bit of information from the extension code and also from this comment.

[dai-shi]

@jose-vale Thanks for pointers.

Could anyone else test the codesandbox build and give 👍 ?
https://ci.codesandbox.io/status/pmndrs/zustand/pr/373/builds/123549

[dai-shi]

The code looks good to me.

[dai-shi]

Okay, let's merge this and see how it goes.

@jose-vale Thanks for your contribution. I like the video with the bear, btw.

[dai-shi]

https://twitter.com/dai_shi/status/1386838502537515008 🐻