feat: add sendCommand, improve typing

[frenautvh]

Hello,

This PR introduces a "sendCommand" method to invoke commands programmatically, here is a sample usage :

import { useEffect, useRef } from "react";
import { ReactTerminal, type ReactTerminalHandle } from "react-terminal";

const commands = {
  cd: (directory: string) => `changed path to ${directory}`
};

function App() {
  const termRef = useRef<ReactTerminalHandle>(null)

  useEffect(() => {
    setTimeout(() => {
      termRef.current?.sendCommand("cd foo")
    }, 3000)
  }, [])

  return (
    <ReactTerminal
      commands={commands}
      welcomeMessage="hello world"
      ref={termRef}
    />
  );
}

export default App;

I also noticed that the typing was not correctly exported on ReactTerminal component, this PR should also fix this issue.

[frenautvh]

this PR should fix #333

[frenautvh]

Hi @bony2023, just wanted to kindly follow up on this PR. Please let me know if there’s anything I can do to help move it forward. Thanks for your time and for maintaining this project! 🙏