On the server side, you can use any preinstalled package, or create your own Python 3.10 environment.
On the client side, you can use any javascript library available from any CDN, or you can include the source code in the app.
My apps include Excel files and test folders that I add after cloning the app to my computer, stuff that is only used while developing and testing offline. You can add any library, just try to avoid including too much stuff that you don’t need.