refactor: support Lumo/Aura switching in examples (internal)

[vursen]

1. Refactored the docs to apply the theme styles per example instead of globally.
2. Added internal support for switching between Lumo and Aura in examples. The UI will be added separately.

[github-actions]

AI Language Review

- In the newly added `applyTheme` function within the `vafctheme.js` file, ensure that `host.matches('[theme~="aura"]')` checks are optimized to only rely on necessary logic and consider refactoring if any redundancy is found.
- Review the `transform` function in the `customConfig` object within the `vite.config.js` file to ensure concise syntax. Specifically, consider the logic used within filter checks to possibly optimize performance or readability. Check if any repetitive code segments can be extracted or simplified.

[sissbruecker]

Seems to work well 👍