lp#904212: add missing mimetypes to impress.desktop
lp#904212: add missing mimetypes to impress.desktop

* application/vnd.openxmlformats-officedocument.presentationml.slide
* application/vnd.openxmlformats-officedocument.presentationml.slideshow

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core