Add support for versioned content

[bmorelli25]

Summary

While we're not yet sure what our versioning scheme will look like in 9.0, we know that we're going to need to support versioning in some capacity.

Important

See this internal Google Doc for up-to-date information.

To be determined

• Everything, really
• How many versioning schemes we need to support
• How deployment types play into versioning
• And more! (see google doc)

Potential Requirements

This list comes from a previous versioning requirement doc. Do not take this as fact.

• We will likely need to support multiple version schemes, for example, the Elastic Stack versioning scheme and other secondary versioning schemes, like for APM agents, integrations, and more.
• It should be obvious when a user is viewing documentation for the current version.
• It should be obvious when a user is viewing documentation for a previous version.
• It should be easy for users to navigate between versions—even if the current page that they are on does not exist in the version they are navigating too.
• It should be possible to link between versioned content and links should be checked to ensure they work.