Convert NPM package to TS

[markerikson]

This PR attempts to fork the the redux-devtools-extension NPM package and convert it to TypeScript:

• renamed redux-devtools-extension to @reduxjs/redux-devtools-extension-fork
• Added TSDX for build tooling, and copied setup from Redux Toolkit
• Added index.ts entry point

Apparently TSDX does not support multiple entry points atm ( jaredpalmer/tsdx#175 ), but we only rely on the one entry point in RTK anyway.

I've already gone ahead and published this package as 0.0.1 on NPM ( https://www.npmjs.com/package/@reduxjs/redux-devtools-extension-fork ), to help verify that it works as expected with RTK.