Add PowerPoint slideshow mime types

There's a special *.ppsx and *.sldx file type

thumbnail/opendocumentthumbnail.desktop

@@ -34,7 +34,7 @@ Name[zh_CN]=Office 文档
 Name[zh_TW]=Office 文件
 
 X-KDE-ServiceTypes=ThumbCreator
-MimeType=application/vnd.oasis.opendocument.text;application/vnd.oasis.opendocument.text-template;application/vnd.oasis.opendocument.text-master;application/vnd.oasis.opendocument.text-master-template;application/vnd.oasis.opendocument.spreadsheet;application/vnd.oasis.opendocument.spreadsheet-template;application/vnd.oasis.opendocument.graphics;application/vnd.oasis.opendocument.graphics-template;application/vnd.oasis.opendocument.presentation;application/vnd.oasis.opendocument.presentation-template;application/vnd.oasis.opendocument.formula;application/vnd.oasis.opendocument.formula-template;application/vnd.oasis.opendocument.chart;application/vnd.oasis.opendocument.chart-template;application/vnd.openxmlformats-officedocument.wordprocessingml.document;application/vnd.openxmlformats-officedocument.wordprocessingml.template;application/vnd.openxmlformats-officedocument.spreadsheetml.sheet;application/vnd.openxmlformats-officedocument.spreadsheetml.template;application/vnd.openxmlformats-officedocument.presentationml.presentation;application/vnd.openxmlformats-officedocument.presentationml.template;application/oxps;application/vnd.ms-xpsdocument;application/vnd.ms-printing.printticket+xml
+MimeType=application/vnd.oasis.opendocument.text;application/vnd.oasis.opendocument.text-template;application/vnd.oasis.opendocument.text-master;application/vnd.oasis.opendocument.text-master-template;application/vnd.oasis.opendocument.spreadsheet;application/vnd.oasis.opendocument.spreadsheet-template;application/vnd.oasis.opendocument.graphics;application/vnd.oasis.opendocument.graphics-template;application/vnd.oasis.opendocument.presentation;application/vnd.oasis.opendocument.presentation-template;application/vnd.oasis.opendocument.formula;application/vnd.oasis.opendocument.formula-template;application/vnd.oasis.opendocument.chart;application/vnd.oasis.opendocument.chart-template;application/vnd.openxmlformats-officedocument.wordprocessingml.document;application/vnd.openxmlformats-officedocument.wordprocessingml.template;application/vnd.openxmlformats-officedocument.spreadsheetml.sheet;application/vnd.openxmlformats-officedocument.spreadsheetml.template;application/vnd.openxmlformats-officedocument.presentationml.presentation;application/vnd.openxmlformats-officedocument.presentationml.template;application/vnd.openxmlformats-officedocument.presentationml.slideshow;vnd.openxmlformats-officedocument.presentationml.slide;application/oxps;application/vnd.ms-xpsdocument;application/vnd.ms-printing.printticket+xml
 
 X-KDE-Library=opendocumentthumbnail
 CacheThumbnail=true