docs: Update Theme switching docs and add visual content

[DevTKSS]

GitHub Issue (If applicable): #

PR Type

What kind of change does this PR introduce?

• Documentation content changes

What is the current behavior?

What is the new behavior?

updated to latest used version

PR Checklist

Please check if your PR fulfills the following requirements:

• Docs have been added/updated which fit documentation template. (for bug fixes / features)

Other information

Internal Issue (If applicable):

[Copilot]

Pull Request Overview

This PR updates the Theme switching documentation to include enhanced functionality and visual content. The changes demonstrate a more reactive approach to theme management and provide visual feedback for users.

• Updates theme options implementation to use IListFeed with selection state
• Adds documentation for listening to theme changes with event subscription
• Includes visual demonstration through a GIF and updated source code references

Comments suppressed due to low confidence (1)

doc/extensions/ThemeService.md:76

• The event name 'ThemeChanged' is inconsistent with the method name 'OnThemeChanged' mentioned in line 70. Based on the method signature in line 79, the event should be named 'OnThemeChanged' or the method should be renamed to match 'ThemeChanged'.

        _themeService.ThemeChanged += OnThemeChanged; // Subscribe to theme changes