Add all missing dependencies to Rasa Playground onLiveCodeChange callback function

[alwx]

Proposed changes:

• fix https://github.com/RasaHQ/playground/issues/129

Status (please check what you already did):

• added some tests for the functionality
• updated the documentation
• updated the changelog (please check changelog for instructions)
• reformat files using black (please check Readme for instructions)

[gausie]

There is a slight change you can make here to reduce dependencies and thus reduce redefinitions of onLiveCodeChange and thus reduce rerenders. I would do it (I think! I haven't tested this) but it's up to you.

if (chatState === "ready") {
      clearPollingInterval();
      setChatState("needs_to_be_retrained");
      updateChatBlock();
    }

can be changed to something like

setChatState(cs => {
  if (cs !== "ready") return cs;
  clearPollingInterval();
  updateChatBlock();
  return "needs_to_be_retrained";
});

If updateChatBlock needs to change after chatState changes, you can do it in an effect.

The same as the above goes for hasStarted.

[alwx]

To be fair, I think a big bunch of what's going on inside prototyper.jsx needs refactoring. I would prefer not to change much right now especially since it might break something but would definitely work on this later.