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/services/networking/vsftpd.nix

@@ -120,7 +120,9 @@ in
       };
 
       userlistFile = mkOption {
+        type = types.path;
         default = pkgs.writeText "userlist" (concatMapStrings (x: "${x}\n") cfg.userlist);
+        defaultText = "pkgs.writeText \"userlist\" (concatMapStrings (x: \"\${x}\n\") cfg.userlist)";
         description = ''
           Newline separated list of names to be allowed/denied if <option>userlistEnable</option>
           is <literal>true</literal>. Meaning see <option>userlistDeny</option>.