fix: Fix packaging to include submodules like backbone

[RafaelMuijsert]

Fix packaging to include submodules like backbone

Description

This PR updates pyproject.toml to ensure all submodules (such as backbone) are properly included when installing zonos.

Changes

• Updated [tool.setuptools.packages.find] in pyproject.toml to:

  [tool.setuptools.packages.find]
  include = ["zonos", "zonos.*"]
  

Why?

Currently, installing Zonos with uv, i.e.: uv add git+https://github.com/Zyphra/Zonos will not fetch the backbones submodule, which means the provided example cannot be run since from zonos.model import Zonos fails.