[Docs] Update all code blocks to toggle between TS and JS syntax

The RTK docs currently use Lenz Weber's https://github.com/phryneas/remark-typescript-tools plugin to let us write TS syntax in code blocks, compile away the TS syntax to plain JS, and show both versions as a tab, as seen at https://redux-toolkit.js.org/api/createSlice:

We ought to start doing the same thing for the RTK docs.

The relevant RTK docs build config is at https://github.com/reduxjs/redux-toolkit/blob/818efb9c9e46df23c891feaab869d72f2d9ecc35/website/docusaurus.config.js#L12-L53 .

We might also want to look at https://shikijs.github.io/twoslash/ , which is built by one of the TS devs. Lenz has said he'd like to investigate switching the RTK docs over to that at some point, so worth considering now.