docs: update readme

Author: aitemr

README.md

@@ -14,7 +14,7 @@ I hope that my codes will help you to solve some problems.
 
 - [ ] [Creational](https://refactoring.guru/design-patterns/creational-patterns)
  - [x] [Singleton](https://github.com/aitemr/design-patterns/tree/master/Creational/Singleton.playground)
-- [ ] Factory Method
+- [X] [Factory Method](https://github.com/aitemr/design-patterns/tree/master/Creational/Factory.playground)
 - [ ] Abstract Factory
 - [ ] Builder
 - [ ] Prototype