Navigating between versions from a module page with a changed location shows an error page

[IgnatBeresnev]

Originally reported to ktor's issue tracker: KTOR-6536

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If a module has changed locations in different versions, when navigating between the versions from the module page a "Not found" error is shown. This makes it look like there is no documentation for the selected version at all. Is it possible to redirect to the new location? Or at least keep the navigation layout and show a "Not found" message in the main content area.

Steps to reproduce:

1. Navigate to ktor-server-core/io.ktor.server.engine.

2. Use the switcher from the top navigation to change the version to 2.3.6.
   The following page is shown: https://api.ktor.io/not-found-version.html?v=2.3.6

[IgnatBeresnev]

This issue might turn into a feature, as maybe, instead of solving this particular issue with module relocation (might be tough to tell if it was relocated or a new one was created), we could address it on a larger scale. For instance, by providing an ability to add hardcoded redirects between pages, so that you can mark specific symbols as relocated, and possibly not only for the versioning plugin.