update readme

README.md

@@ -27,7 +27,7 @@ dependencies {
 ## Usage
 
 First of all, BindingExtension using refelction a lot to link many things internally in order to provide simple usage.
-To prevent having trouble with proguard, please remember to exclude ViewBinding related class in your proguard file.
+To prevent having trouble with proguard, please remember to exclude `ViewBinding` related class in your proguard-rules file.
 For example, if your ViewBinding class is all under `com.jintin.bindingextension.app` package:
 ```
 -keep public class com.jintin.bindingextension.app.databinding** { <methods>; }