Add support for versioned documentation

[alexskr]

Current Limitation: All documentation is currently published for the latest version only, with no way to view docs for previous releases.

[jonquet]

The proposal @alexskr in 2024 Workshop Report was that we adopt a custom "User guide" per portal. In other words, the User guide is not versionned but customized portal by portal.

For the Admin guide, the recent proposal is to adopt the shared documentation approach (already adopted for User guide) but not fors portal specific docs, but instead for Appliance specific docs... VA3, VA4, VA-AgroPortal etc...
We should work with @MajidFiaz towards this soon