Added lospec palette scheme handler

assets/flatpak/net.pixieditor.PixiEditor.desktop

@@ -7,7 +7,7 @@ StartupWMClass=pixieditor
 Terminal=false
 Type=Application
 Categories=Graphics;2DGraphics;RasterGraphics;VectorGraphics
-MimeType=application/x-pixi;image/jpeg;image/png;image/gif;image/bmp;image/webp;image/svg+xml;font/otf;font/ttf;
+MimeType=application/x-pixi;image/jpeg;image/png;image/gif;image/bmp;image/webp;image/svg+xml;font/otf;font/ttf;x-scheme-handler/lospec-palette;
 GenericName=2D Editor
 SingleMainWindow=true
 Keywords=editor;image;2d;graphics;design;vector;raster;