title: react-testing-library - appending characters to an input or text area
body: <p>I have a use case where I need to type a few characters into a text area, test something, and then append more characters into that text area. How do I do this? If I call <code>fireEvent.change()</code> twice in succession, the second call overwrites the content, instead of appending to it.</p>
  <pre><code>fireEvent.change(getByTestId('text-txt-area'), {
      target: { value: '123' }
  });
  
  // Overwrites '123' instead of appending '456'
  fireEvent.change(getByTestId('text-txt-area'), {
      target: { value: '456' }
  });
  </code></pre>