feat: warn unknown options

[kricsleo]

resolves https://github.com/unjs/citty/issues/201

This PR adds support for warning about unknown options.
This is enabled by default but can be disabled by setting meta.allowUnknownOptions: true.

[codecov[bot]]

Codecov Report

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Additional details and impacted files

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##             main     #202   +/-   ##
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  Coverage        ?   94.18%           
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  Files           ?        8           
  Lines           ?      533           
  Branches        ?      178           
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  Hits            ?      502           
  Misses          ?       31           
  Partials        ?        0           

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