Work in progress
This patch adds 2 help pages for the document themes dialog and document theme color dialog.
Contents will be added later.
Change-Id: Ia357a30e6c749898a3a636eba922bd1629c3249f
Reviewed-on: https://gerrit.libreoffice.org/c/help/+/154941
Tested-by: Jenkins
Reviewed-by: Olivier Hallot <olivier.hallot@libreoffice.org>