Versal's Code gadget is a fully functioning IDE. When you add the gadget to your Versal content, you start in the Editor. The html file is needed for the IDE to run properly. You can't delete it, but you can change the contents of the file to suit your needs.
Add files by clicking the blue "+" button in the left corner of the Editor.
Once you begin adding files, use the html file to call your other files. Here, we are adding a script tag to call our index.js file.