iPhone 13 case - multi functions

I took jwalker55's iphone 13 case, and cut a female thread to the back. Now the case can have multiple functions simply by changing attaching different male threads.

I uploaded a few use cases that I can think of:

1. a thread with toad stencil (credit to Longquang)
2. a thread with stencil "Z" for decoration.
3. a thread with a baseball bat attached, so that it can work as a support for phone stand.
4. a thread with a mount adapter for tripod.
5. a plain thread that you can attach your own models
6. a thread with Mario stencil (credit to Longguan)
7. a thread with Peach stencil (credit to Longguan)

python source code for generating the model:
https://github.com/mingyuanzhang/python3d/blob/main/src/iphone13_case.py