Proposal: Modernize the landing page and docs UI

The documentation site works well in terms of content, but the overall visual design feels quite outdated compared to modern documentation sites like VitePress or Docusaurus.

The landing page (https://moment.github.io/luxon/#/) in particular feels very sparse — it has a lot of empty space and doesn't really showcase what Luxon can do at first glance.

I'd love to propose a full visual redesign to give the site a more modern, polished look and feel. Nothing that changes the content or structure — just a cleaner, more up-to-date design.