Native support in Python 3.14

Hello, I believe the CLI provided by this package is natively supported thanks to [PEP 784](https://peps.python.org/pep-0784/).

Starting from Python 3.14, you can do:
```sh
python -m tarfile --extract filename.tar.zst
python -m tarfile --extract filename.tar.zst targetdir
```

For older versions of Python, you can use [the backport](https://github.com/rogdham/backports.zstd):
```sh
python -m pip install backports.zstd
python -m backports.zstd.tarfile --extract filename.tar.zst
python -m backports.zstd.tarfile --extract filename.tar.zst targetdir
```

You probably already know about the integration of Zstandard in the standard library, but I wanted to mention it just in case 🙂

Start by reading PEP 784 and the linked Python 3.14 tarfile commands. The report names no repository files or tests and requests no specific change, so first clarify whether documentation or package-direction work is intended before implementation.

Written by the indexing model from the issue text.