Indicate collection version for each library version

Going through the docs right now, it's tough for a user to know how each library version maps to each Ignition collection.

For example, if I land on `ign-gui`'s [entry point](https://ignitionrobotics.org/libs/gui), it tells me `3.2.0` on the top. But is that Blueprint, Citadel? As an end user, should I need to know the exact `ign-gui` version I'm using?

Then if I click on the "Versions" tab, I'm offered several options. It would be good to have an indication of which of them refer to a collection, which are LTS and which are EOL.

Also, once I'm inside [a library's API docs](https://ignitionrobotics.org/api/gui/3.2/index.html), it would be nice to know which collection that is.