Add all 23 GoF design pattern implementations

02-structural/decorator/TextProcessor.java

@@ -0,0 +1,9 @@
+package decorator;
+/**
+ * Component — defines what all text processors do.
+ * Both the base implementation AND every decorator implement this.
+ * Sharing this type is what makes decorators stackable.
+ */
+public interface TextProcessor {
+    String process(String text);
+}