Add status state for useChat (ready, submitted, streaming, error)

[nikas-belogolov]

Add a status state for useChat hook, which can be used to display for the user the current state of the chat.

How I currently implement such status state:

const [status, setStatus] = useState<ChatStatus>("ready");
const textOptions = createChatClientOptions({
	connection: fetchServerSentEvents("/api/chat"),
	onLoadingChange: (isLoading) => {
		setStatus(isLoading ? "streaming" : "ready");
	},
	onFinish: () => {
		setStatus("ready");
	},
	onError: () => {
		setStatus("error");
	},
})

const { messages, sendMessage, isLoading, error } = useChat(textOptions);

It would be good if the useChat hook would return also a status state like such:

const { messages, sendMessage, status } = useChat(textOptions);