Communicate future version availability and clarify versioning behavior

[KOTungseth]

Description

With the release of future versions of the Elastic Stack, we need to make sure users understand that elastic.co/docs includes documentation for both 9.0.0 and future 9.x minor versions.

Our current version dropdown says Current version (9.0+), which may lead users to believe that future 9.x minor version docs aren’t available yet. Since we've moved to a unified minor version model starting with 9.0.0, we need to make that model clear and visible.

Create dedicated Elastic Docs versioning FAQ page

Change Understanding versioning and availability into an FAQ, including the following:

• Q: Where can I find documentation for Elastic Stack {future version}?
  You’re in the right place! All documentation for Elastic Stack 9.0.0 and later lives at elastic.co/docs. That includes {latest version}, and any future minor versions in 9.x.

• Q: Why doesn’t Elastic have separate documentation for {latest version}?
  Starting with Elastic Stack 9.0.0, we no longer publish separate documentation for each minor release. Instead, we keep all 9.x changes in a single, continuously updated documentation set.
  This reduces duplication across pages, helps you see the full evolution of a feature, and simplifies search and navigation.

• Q: How do I know which content was added in a specific version?
  We mark all new or changed content with clear callouts like this:
  {include badge examples here}
  These inline version markers help you spot what’s new without switching between versions.

• Q: What if I’m using a version earlier than 9.0.0?
  Documentation for Elastic Stack 8.19.0 and earlier is available at elastic.co/guide.

• Q: How often is the documentation updated?
  We update elastic.co/docs regularly with:

  • Minor version changes (e.g., 9.1.0)
  • Patch-level updates (e.g., 9.1.1)
  • Continuous improvements to clarify and expand guidance
    For the latest changes, check the release notes for each product.

• Q: How do I know what the “current” version is?
  The version dropdown at the top of the page will always show the latest available 9.x version. For example:
  Elastic Stack 9.0+ (latest: 9.1.0) or Version 9.0+ (latest: 9.1.0)
  You can use this to confirm you’re viewing the most up-to-date docs.

Update Release notes landing page

Current: Learn about the latest changes, issues, fixes, and deprecations for Elastic releases, including Elastic Stack 9.0 and Elastic Cloud Serverless, by reviewing the release notes.

Proposed change: Learn about the latest changes, issues, fixes, and deprecations for Elastic releases. The release notes cover Elastic Stack 9.0.0 and later, including the latest 9.1.0 release, as well as Elastic Cloud Serverless.