[Contribute] Improved documentation website

[radiorambo]

Hello, I am a web developer and want to build a documentation site for distrobox. I have looked into already existing docs, it's functional but can be improved with built in search, better page organisation and many small quality of life improvements.

I have also checked a previous PR #1565 for improving distrobox website, in which your two main concerns were, if i understood correctly,

1. Preserve the /docs location, to stay in sync with man pages and website.
2. Avoid custom syntax (e.g., frontmatter like +++ title = ... [extra] toc = true +++) that breaks table of contents, navigation, and readability when viewing Markdown files directly on GitHub/GitLab.

By keeping above things in mind, I am planning to use VitePress, which uses the existing markdown files in docs folder to build documentation while respecting your above concerns. It auto deploys and one time setup without much maintenance. But if you have any other suggestion, I am open to discuss.

So if you are OK with this Idea, I will start the work.

Recently built similar documentation site for rmcrackan/Libation#1498 and sinelaw/fresh#844