Advertise WebP read support for showfoto via .desktop file

Signed-off-by: Alex Kent Hajnal <software@alephnull.net>
(cherry picked from commit ec8d2e6413)

digikam/showfoto/showfoto.desktop

@@ -145,7 +145,7 @@ Comment[zh_TW]=運用開放原始碼的力量像專業人士般管理您的照
 Exec=showfoto %i -caption "%c" %U
 Icon=showfoto
 Type=Application
-MimeType=image/gif;image/x-xpm;image/x-xbm;image/jpeg;image/png;image/tiff;image/x-bmp;image/x-psd;image/x-eim;image/x-portable-bitmap;image/x-portable-pixmap;image/x-portable-greymap;image/x-raw;
+MimeType=image/gif;image/x-xpm;image/x-xbm;image/jpeg;image/png;image/webp;image/tiff;image/x-bmp;image/x-psd;image/x-eim;image/x-portable-bitmap;image/x-portable-pixmap;image/x-portable-greymap;image/x-raw;
 Terminal=false
 Categories=Qt;TDE;Graphics;
 X-DocPath=showfoto/index.html