[Docs Rewrite] Create "Treat Reducers as State Machines" page

[bolatovumar]

What docs page is being added or updated?

This bit: https://redux.js.org/style-guide/style-guide/#treat-reducers-as-state-machines

• Section: #treat-reducers-as-state-machines
• Page: Redux Style Guide

For Updating Existing Content

What updates should be made to the page?

Add detailed explanation for "Treat Reducers as State Machines" section

Do these updates change any of the assumptions or target audience? If so, how do they change?

No, but it would make it easier to understand with a code example provided.

[bolatovumar]

I'm willing to submit a PR for this if acked.

[markerikson]

Yeah, this ties into #3598 . I know @davidkpiano had offered to try writing that page.

[davidkpiano]

@bolatovumar I can help review, if you'd like! If I were to write it, it would basically be a distillation of this: https://dev.to/davidkpiano/redux-is-half-of-a-pattern-1-2-1hd7 (ignore the article title)

[bolatovumar]

@davidkpiano if you are on it then that's great. Your example from the article is great. Your article what got me to open this issue as the docs weren't anywhere as clear as your writeup.