Add directives for class, style, Alpine.js, HTMX

Hi, thank you for providing this awesome library! I have enriched the library, so any developer can user some helpers for building common HTML attributes (class, style as a start), but also some powerful javascript libraries that are based on setting special HTML attributes (Alpine.js, HTMX). You can have a look in the updated [README.md / Using directives](https://github.com/nikalexis/dominate/tree/directives-rc-1.0.0?tab=readme-ov-file#using-directives) for code examples using the new features. In case you think this is a good idea, I will be glad to discuss any guidelines you have in order to accept it in your master (upstream) branch / release cycle.