Add Version 6 docs subdomain and link

[TheAlexLichter]

Documentation is

• Missing
• Outdated
• Confusing
• Not sure?

Explain in Detail

Subdomains for previous major versions from v5 to v2 are linked in the Navbar. v6 is missing at the moment

Your Suggestion for Changes

Create the v6.vite.dev subdomain with the latest v6 docs and link it there

Reproduction

No response

Steps to reproduce

No response

[patak-dev]

Thanks for the heads up! Evan is setting up the subdomain later today and then we'll merge:

• docs: add vite 6 docs to version dropdown #20291