Merge pull request #247129 from khaneliman/graphics-mainProgram

pkgs/applications/graphics/digikam/default.nix

···
     license = licenses.gpl2;
     homepage = "https://www.digikam.org";
     platforms = platforms.linux;
+    mainProgram = "digikam";
   };
 }

pkgs/applications/graphics/feh/default.nix

···
     license = licenses.mit-feh;
     maintainers = with maintainers; [ viric willibutz globin ma27 ];
     platforms = platforms.unix;
+    mainProgram = "feh";
   };
 }

pkgs/applications/graphics/inkscape/default.nix

···
     license = licenses.gpl3Plus;
     maintainers = [ maintainers.jtojnar ];
     platforms = platforms.all;
+    mainProgram = "inkscape";
     longDescription = ''
       Inkscape is a feature-rich vector graphics editor that edits
       files in the W3C SVG (Scalable Vector Graphics) file format.