fix missing desktop files for mpv and helix

lib/default.nix

@@ -12,17 +12,23 @@
       configArg ? "-c ",
       excecutable ? "${package}/bin/${name}",
     }:
-    pkgs.writeShellApplication {
+    pkgs.symlinkJoin {
       inherit name;
+      paths = [
+        (pkgs.writeShellApplication {
+          inherit name;
 
-      runtimeInputs = [ package ];
+          runtimeInputs = [ package ];
 
-      text = ''
-        if test -r "${userConfig}"; then
-          exec -a "$0" "${excecutable}" "$@"
-        else
-          exec -a "$0" "${excecutable}" ${configArg}"${globalConfig}" "$@"
-        fi
-      '';
+          text = ''
+            if test -r "${userConfig}"; then
+              exec -a "$0" "${excecutable}" "$@"
+            else
+              exec -a "$0" "${excecutable}" ${configArg}"${globalConfig}" "$@"
+            fi
+          '';
+        })
+        package
+      ];
     };
 }