How do I make a JavaScript editor, html editor, and css editor in html

Ive been trying to find some code for three of these editors. I’m making a huge update to my app kitty cat for developers and I wanted to add more programming languages the app is made in appcreator24 and you can’t download in apps made in that website and the only code app creator supports is html

I was expecting to find a GitHub page with open source code but nothing was there