Describe the use-case for this feature

Currently only the spec which was built latest is shown on the website. This creates two problems:

• it is not easily possible to read the specification of an older version
• pushing an update to an older version will replace what's currently published. For example, after publishingv2.1.1 the docs for v2.2.0 disappeared from the website.

What do you propose

Something like LSP does:https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#lsp

I've checked to make sure there isn't already a way to support this in the current protocol

• I've checked the existing protocol and there isn't a way to do this currently

Maintainer approval (This is for the maintainers)

• Jetbrains
• Metals
• Scala Center