Serving a 'create-react-app' made files with Flask backend

I'm trying to change the backend of my React app to be only Flask based, instead of having two different servers ('npm' and 'flask').

The app was created with 'create-react-app' and the current folder structure is:

- myapp
  - node_modules
  - src
    - App.js
    - index.js
    - index.css
    - App.css
  - templates
    - index.html
  app.py
  package.json

The app.py file consists of this code:

from flask import Flask, render_template

app = Flask(__name__)

@app.route('/')
def index():
    return render_template('index.html')

if __name__ == '__main__':
    app.run(debug=True)

The thing is, until now on every save, the npm automatically bundled and reloaded all of my changes in the browser. Now, if I make a change, for example, in the 'index.html', the change is visible in the browser. However, if I try to edit my 'App.js', the change isn't visible at all.

From now on, do I need to rebundle the 'App.js' and components by myself everytime I save them?

I'm a bit confused about this one, so any help or advice would be highly appreciated.