Updated Roadmap with reference to Configurations.

Closes #4

README.md

@@ -123,7 +123,8 @@ As of right now, **they are not planned**, but there is possibility in the futur
 While it being such a huge project, **YAGL** can still be expanded a lot.
 These are some of the pending features that are planned for the future:
 
-- [ ] possibility to serialize data to **different file formats** like **JSON**, **XML**, **properties**;
+- [x] possibility to serialize data to **different file formats** like **JSON**, **XML**, **properties**.
+      Completed using the [Configurations library](https://github.com/Fulminazzo/Configurations);
 - [ ] add support for [PlaceholderAPI](https://github.com/PlaceholderAPI/PlaceholderAPI) in variable replacements;
 - [ ] a special `GUIContent` that allows animated items;
 - [ ] a special `GUIContent` that allows items which can be toggled based on user click;