[WIP] Add sticky group header to Select component

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

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This section details on the original issue you should resolve

<issue_title>Select - sticky group header</issue_title>
<issue_description>## Description

Add a sticky group header to Select component.

e.g. display all the time that English is official

<agent_instructions>udělej možnost v Select komponentě mít sticky header. Navrhni to tak abychom nemuseli předělávat všechny select komponenty a zároveň aby to bylo čisté a čitelné řešení.</agent_instructions>

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