Added mime

assets/flatpak/net.pixieditor.PixiEditor.desktop

@@ -6,6 +6,7 @@ Exec=pixieditor.sh %u
 StartupWMClass=pixieditor
 Terminal=false
 Type=Application
+MimeType=application/x-pixi
 Categories=Graphics;2DGraphics;RasterGraphics;VectorGraphics
 GenericName=2D Editor
 SingleMainWindow=true