sitemap: added support for custom urls on standard pages
sitemap: added support for custom urls on standard pages

MarkusH/pelican-plugins,MarkusH/pelican-plugins,mikitex70/pelican-plugins,mortada/pelican-plugins,talha131/pelican-plugins,mikitex70/pelican-plugins,mortada/pelican-plugins,talha131/pelican-plugins,talha131/pelican-plugins,mikitex70/pelican-plugins,MarkusH/pelican-plugins,mortada/pelican-plugins,mikitex70/pelican-plugins,mortada/pelican-plugins,MarkusH/pelican-plugins,MarkusH/pelican-plugins,talha131/pelican-plugins,mortada/pelican-plugins,talha131/pelican-plugins