Added outline for structural design patterns.

README.md

@@ -101,6 +101,52 @@ TODO
 
 ## Structural Design Patterns
 
+In plain words:
+
+> Structural patterns are mostly concerned with object composition or in other
+words how the entities can use each other. Or yet another explanation would be,
+they help in answering "How to build a software component?"
+
+Wikipedia says:
+
+> In software engineering, structural design patterns are design patterns that
+ease the design by identifying a simple way to realize relationships between
+entities.
+
+ * [Adapter](#-adapter)
+ * [Bridge](#-bridge)
+ * [Composite](#-composite)
+ * [Decorator](#-decorator)
+ * [Facade](#-facade)
+ * [Flyweight](#-flyweight)
+ * [Proxy](#-proxy)
+
+### 🔌 Adapter
+
+TODO
+
+### 🚡 Bridge
+
+TODO
+
+### 🌿 Composite
+
+TODO
+
+### ☕ Decorator
+
+TODO
+
+### 📦 Facade
+
+TODO
+
+### 🍃 Flyweight
+
+TODO
+
+### 🎱 Proxy
+
 TODO
 
 ## Behavioral Design Patterns