Improve package pages: list past/future package versions

[fingolfin]

Right now package pages like https://www.gap-system.org/Packages/ace.html only show the package version distributed in the latest GAP release, e.g.:

Version with GAP 4.11.1: 5.3 (Released 12/02/2020)

It would be nice if also showed...

1. the "latest" version (if it changed in the distribution after the last GAP release)
2. the version(s) bundled with older GAP releases.

Regarding point 1: this ties in with issue #234. To implement it, we would add another file _data/package-infos/latest.json which is generated like _data/package-infos/4-11-1.json etc. from the same script (which may need to be adjusted; also, it maybe can be run at the same time as the package distribution tarballs are updated).

Regarding point 2: of course we just need to loop over all past GAP releases to gather the info. But not all users may want to see it. Some ideas for that:

• we can hide this info by default e.g. via HTML <details> elements
• we can "compress" it: instead of showing something like this (data is made up)

  Version with GAP 4.10.2: 5.3
  Version with GAP 4.10.1: 5.3
  Version with GAP 4.10.0: 5.3
  Version with GAP 4.9.3: 5.3
  Version with GAP 4.9.2: 5.2
  

• we could show

  Version with GAP 4.9.3 - 4.10.2: 5.3
  Version with GAP 4.9.2: 5.2
  

[fingolfin]

We essentially decided against doing this when we did the new website design in PR #339. We'll focus on the present. Studying past data is cool, but if someone really wants that, they'll have to implement it themselves.