Indicate collection version for each library version

[chapulina]

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, 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, it would be nice to know which collection that is.