Add missing 'type', 'defaultText' and 'literalExample' in module definitions

- add missing types in module definitions
- add missing 'defaultText' in module definitions
- wrap example with 'literalExample' where necessary in module definitions

nixos/modules/system/boot/loader/grub/grub.nix

@@ -251,6 +251,7 @@ in
       };
 
       extraFiles = mkOption {
+        type = types.attrsOf types.path;
         default = {};
         example = literalExample ''
           { "memtest.bin" = "''${pkgs.memtest86plus}/memtest.bin"; }

nixos/modules/system/boot/loader/grub/ipxe.nix

@@ -39,7 +39,7 @@ in
               dhcp
               chain http://boot.ipxe.org/demo/boot.php
             ''';
-          };
+          }
         '';
       };
     };