found typo that is marked as . instead of ','

Author: gg582

src/languages/freedesktop.js

@@ -61,7 +61,7 @@ export default function(hljs) {
 
   return {
     name: 'FreeDesktop configuration format',
-    aliases: ['desktop', 'service', 'mount', 'socket', 'timer', 'nmconnection', 'systemd'. 'freedesktop'],
+    aliases: ['desktop', 'service', 'mount', 'socket', 'timer', 'nmconnection', 'systemd', 'freedesktop'],
     case_insensitive: false,
     contains: [
       COMMENT,