add hot reload modules for templates

[UseMuse]

for example

import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
import * as serviceWorker from './serviceWorker';

const rootEl = document.getElementById('root')

ReactDOM.render(
  <App />,
  rootEl
)

if (module.hot) {
  module.hot.accept('./App', () => {
    const NextApp = require('./App').default
    ReactDOM.render(
      <NextApp />,
      rootEl
    )
  })
}

// If you want your app to work offline and load faster, you can change
// unregister() to register() below. Note this comes with some pitfalls.
// Learn more about service workers: https://bit.ly/CRA-PWA
serviceWorker.unregister();

[penx]

A duplicate of #4732, but I agree there should at least be a statement on HMR within the readme, even if that's to state why they suggest against it.

[penx]

This also works:

if (module.hot) {
  module.hot.accept()
}

Would be good to list any caveats of doing this rather than theaccept('./App' approach.

[penx]

Hot module reloading has been superseded by react-refresh and its webpack plugin which was merged in April. It is not yet released (latest release, 3.4.1, was in March), but will hopefully be in >=3.4.2. In master it is currently marked as experimental and behind the FAST_REFRESH flag.