Add anchor for Usage title

README.md

@@ -25,7 +25,7 @@
     - react-native-svg >= 3.2.0 only supports react-native >= 0.29.0
     - react-native-svg >= 4.2.0 only supports react-native >= 0.32.0
     - react-native-svg >= 4.3.0 only supports react-native >= 0.33.0
-    
+
 2. Link native code
 
     ```bash
@@ -39,7 +39,7 @@
     rnpm link react-native-svg
     ```
 
-### Usage
+### <a name="Usage">Usage</a>
 
 Here's a simple example. To render output like this: