I would like to share with you a simple example of implementing a feature for cropping images with fingers.
Managing pictures in Thunkable is where I spent a lot of weeks and I wanted to give back something that I hope can help some of you.
You can then use the Thunkable web extension to post messages and receive messages to interact with the “native” part of the app (you can take inspiration from this other project, thanks to @muneer for help).
Please, pay attention to asking user permission correctly. Indeed, your app needs permission to use the camera and access the photo library but the HTML / js script, unfortunately, does not do this.
For this purpose, I suggest you read this discussion to get inspiration.
Pay attention to FileRobot licensing because there are restrictions on how you use the library.