[Lazarus] Attn. Don, documentation snapshots via CI

[Maxim Ganetsky]

Hello.

As a first step of solving outdated documentation snapshot issue 
(https://gitlab.com/freepascal.org/lazarus/lazarus/-/issues/40032 ) I 
propose to generate it as an artifact of CI job (in `main` branch for 
now), which then can be uploaded wherever we want.

So I have the following questions:

1. FPDoc from which FPC version is preferred (from `main` branch I guess)?
2. Where rtl.xct and fcl.xct should be obtained? Should FPC 
documentation be built first?
3. Should we build HTML, CHM or both?
4. Are there any dependencies beyond Lazarus, FPC and their sources?

-- 
Best regards,
  Maxim Ganetsky                  mailto:ganmax at narod.ru