`typing_extentions` missing from dependencies.

[coltonbh]

Describe the bug

xtb will not run after an installation using conda or pip because it is missing the typing_extensions dependency.

Traceback (most recent call last):
  File "/home/cbh/dev/personal/qcop/script3.py", line 4, in <module>
    from xtb.interface import Calculator, Param
  File "/home/cbh/.pyenv/versions/miniconda3-4.7.12/envs/xtb2/lib/python3.11/site-packages/xtb/interface.py", line 20, in <module>
    from typing_extensions import Literal
ModuleNotFoundError: No module named 'typing_extensions'

To Reproduce

conda create -n xtb xtb-python -c conda-forge

>>>  from xtb.interface import Calculator, Param

OR

python -m venv env
source env/bin/activate
pip install xtb

>>>  from xtb.interface import Calculator, Param

Expected behaviour

xtb properly specifies its dependencies and can run after an install.