Merge pull request #125378 from nagy/purescript-mainprogram

purescript: add meta.mainProgram

pkgs/development/compilers/purescript/purescript/default.nix

···
     license = licenses.bsd3;
     maintainers = with maintainers; [ justinwoo mbbx6spp cdepillabout ];
     platforms = [ "x86_64-linux" "x86_64-darwin" ];
+    mainProgram = "purs";
   };
 }