Bump version 0.20.0 & update main README.

Author: ilopX

CHANGELOG.md

@@ -1,3 +1,6 @@
+## 0.20.0
+- Add "Conceptual Dialog Factory" example.
+
 ## 0.19.0
 - Add "Conceptual Gui Factory" example.
 

README.md

@@ -4,9 +4,9 @@ It contains **Dart** examples for all classic **GoF** design patterns.
 
 # Implementation checklist:
 - [ ] **Creation**
-    - [ ] **Abstract Factory** [[Conceptual Gui Factory](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/abstract_factory/conceptual_gui_factory)]
+    - [x] **Abstract Factory** [[Conceptual Gui Factory](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/abstract_factory/conceptual_gui_factory)]
     - [x] **Builder** - [[Color Text Format](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/builder/color_text_format)]
-    - [ ] **Factory Method**
+    - [x] **Factory Method** [[Conceptual Platform Dialog](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/factory_method/conceptual_platform_dialog)]
     - [x] **Prototype** - [[Shapes](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/prototype/shapes)] 
     - [ ] **Singleton**
 - [ ]  **Behavioral**

pubspec.yaml

@@ -1,6 +1,6 @@
 name: design_patterns_dart
 description: Dart examples for all classic GoF design patterns.
-version: 0.19.0
+version: 0.20.0
 homepage: https://refactoring.guru/design-patterns
 repository: https://github.com/RefactoringGuru/design-patterns-dart
 issue_tracker: https://github.com/RefactoringGuru/design-patterns-dart/issue