feat: Added support for automatic dark/light mode based on user os settings

[rahulptl165]

Resolves #56 .

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Description

This PR adds a new "Auto" theme option that automatically switches between dark and light modes based on the user’s operating system preferences (using prefers-color-scheme).

changes i've made:

• Updated the THEMES array to include an "Auto" option alongside "Light" and "Dark".
• Modified _onThemeChange to detect OS theme preferences via window.matchMedia('(prefers-color-scheme: dark)') when "Auto" is selected, then apply the appropriate theme (dark or light).

Related Issues

This pull request:

• resolves Support automatic light/dark mode theme based on OS #56
• fixes Support automatic light/dark mode theme based on OS #56

Questions

Any questions for reviewers of this pull request?

No.

Other

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Recording new feature

Screen.Recording.2025-03-08.162444.mp4

No.

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