Bump version 0.13.0.

Author: ilopX

CHANGELOG.md

@@ -1,3 +1,6 @@
+## 0.13.0
+- Add "Observer" pattern from official book, rewritten from Java example.
+
 ## 0.12.19
 - Refactoring: reformatting and minor changes
 

README.md

@@ -16,7 +16,7 @@ It contains **Dart** examples for all classic **GoF** design patterns.
     - [ ] [**Iterator**](https://refactoring.guru/design-patterns/iterator)
     - [ ] [**Mediator**](https://refactoring.guru/design-patterns/mediator)
     - [ ] [**Memento**](https://refactoring.guru/design-patterns/memento)
-    - [ ] [**Observer**](https://refactoring.guru/design-patterns/observer)
+    - [x] [**Observer**](https://refactoring.guru/design-patterns/observer) - [[Open-Close Editor Events](https://github.com/RefactoringGuru/design-patterns-dart/tree/master/patterns/observer/open_close_editor_events)]
     - [ ] [**State**](https://refactoring.guru/design-patterns/state)
     - [ ] [**Template Method**](https://refactoring.guru/design-patterns/template-method)
     - [ ] [**Visitor**](https://refactoring.guru/design-patterns/visitor)

pubspec.yaml

@@ -1,6 +1,6 @@
 name: design_patterns_dart
 description: Dart examples for all classic GoF design patterns.
-version: 0.12.19
+version: 0.13.0
 homepage: https://refactoring.guru/design-patterns
 repository: https://github.com/RefactoringGuru/design-patterns-dart
 issue_tracker: https://github.com/RefactoringGuru/design-patterns-dart/issue