typing_extension requirement is too vague

I just ran into trouble trying to use this awesome lib on a computer whose `typing_extensions` was too old. It was impossible to load richclick, with error `ImportError: cannot import name 'NotRequired' from 'typing_extensions'`. The solution was to upgrade `typing_extensions` on my system.



And indeed the pyproject.toml here simply specify a dependency on `typing_extensions` without any version bound. Could you please put a lower bound there?



My system was on `3.10.0.2` and indeed the [documentation](https://typing-extensions.readthedocs.io/en/latest/#typing_extensions.NotRequired) says that `NotRequired` was added in 3.11. There is no version 3.11 on PyPi, it jumps from 3.10 to 4.0. I just checked that upgrading to 4.0.0 allows to `import rich_click`, but I didn’t try to use it. So you could try requiring `typing_extensions>=4.0.0` and this would already be progress.

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