Versioning: show selector at all levels

[rnett]

Is your feature request related to a problem? Please describe
The version dropdown is only shown at the top level, in my case on the all modules page.

Describe the solution you'd like
All pages should show the version selector, with some way (strikethrough, maybe?) of noting when the page would not be available for those versions.

Additional context
For example, see the official Kotlin docs: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.browser/window.html