Restoration of docs.kde.org

[Johnny Jazeix]

Hi,

The documentation on docs.kde.org, which contains all user
documentation, was not updated for the last years.
After few months of work, we managed to generate again the
applications documentation and the website is now up-to-date.

If your application contains a docbook but is not displayed in the
website, please check if the /gitlab-templates/documentation.yml has
been added in the .gitlab-ci.yml and ensure you are installing the doc
in CMakeLists.txt: kdoctools_install(po).

The modernization of the website was not in scope, there is an issue
opened in https://invent.kde.org/websites/docs-kde-org/-/issues/1.

Cheers,
Ben, Luigi & Johnny