Add the `--version` command line option

[jcouball]

Implement the --version command line option.

• Use the same parser as chezmoi in order to be able to easily be able to parse the command line in the same way that chezmoi does
• Where it makes sense, follow the same code structure as chezmoi so that people familiar with that project can easily pick up this project
• Output the same thing that chezmoi does (but as applied to chezroot). It may be worth seeing how chezmoi implements their version command
• After the above is implemented and tested, after displaying the chezroot version line, run chezmoi to show the chezmoi version
• For now, anything else given on the command line should fail, giving the command line usage (anything other than chezroot --version should fail for now.

Here is an example of the chezmoi --version command line:

$ chezmoi --version
chezmoi version v2.67.0, commit 8591960c5b55b27d3806c6754232e1a6980957e1, built at 2025-11-02T19:38:29Z, built by Homebrew