Add all 23 GoF design pattern implementations

01-creational/abstract-factory/DarkThemeFactory.java

@@ -0,0 +1,14 @@
+package abstractfactory;
+
+public class DarkThemeFactory implements UIFactory {
+
+    @Override
+    public Button createButton() {
+        return new DarkButton();        // Only Dark products come from this factory
+    }
+
+    @Override
+    public TextField createTextField() {
+        return new DarkTextField();
+    }
+}