HelpContent (localhelp) authoring documetation available in our wiki

Hi

For those interested in authoring contents for the help pages, I have
ported the only documentation available on XHP files to the wiki.

The objective is to allow additions or contributions by the community
to the XHP-specific documentation, when new features are proposed and
implemented. The documentation also explains how the local help works in
LibreOffice, when you press the help button in a dialog or when you
press F1.

The book can be acessed in the following URL:

https://wiki.documentfoundation.org/HelpContentAuthoring

If you are already skilled in autoring help contents, you may help us to
update its contents, mark obsolete exerpts, adjust wiki links and more.
It is a an on-going process.

Kind regards.