feat: add auto theme functionality to OverType editor

[dido739]

Hi guys. Yesterday I stumbled upon #84 and decided to do something.
This is what I did:

• Implemented auto theme switching based on system color scheme preference.
• Added auto theme to themes registry, defaulting to solar colors.
• Enhanced setTheme method to handle auto theme and resolved theme application.
• Introduced media query listeners for real-time theme updates.
• Updated example pages to demonstrate auto theme functionality.
• Created tests for auto theme behavior at both instance and global levels.
  Screenshots form the auto theme:
• dark system:

• white system:

Feel free to use this or not.

P.S. Unfortunately the size increased from ~95KB to ~98KB. It could probably be optimized. I'm open to suggestions.

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Summary by cubic

Adds an auto theme that matches the system light/dark setting and switches in real time. Works per-instance and globally via OverType.setTheme('auto'), with optimized listeners, DOM updates, and web component refreshes.

• New Features
  • 'auto' resolves to 'solar' or 'cave' via prefers-color-scheme; real-time switching with a shared matchMedia listener and cleanup on destroy
  • setTheme supports 'auto' at instance and global levels; applies data-theme='auto' and data-resolved-theme; web components refresh correctly
  • Helpers: resolveAutoTheme(), getSystemColorScheme(); internal _updateThemeAttrs syncs DOM
  • New example page and Playwright tests; README/CHANGELOG updated
  • Bundle: min build reduced by ~10KB; final size ~97KB after optimizations

^{Written for commit f8d77e3. Summary will update on new commits.}

[dido739]

Update: After some work with Copilot I've managed to save ~0.9KB, using some optimizations.
List here.