Update README.md

please ignore past commit i mixed up MainActivity and applicationActivity  
import com.cboy.rn.splashscreen.SplashScreenReactPackage;
 is needed for 
protected List<ReactPackage> getPackages()

Author: fenderrex

README.md

@@ -64,6 +64,7 @@ dependencies {
 3.Update the MainApplication.java file to use `react-native-splash-screen` via the following changes:   
 
 ```java
+import com.cboy.rn.splashscreen.SplashScreenReactPackage;
 public class MainApplication extends Application implements ReactApplication {
 
     private final ReactNativeHost mReactNativeHost = new ReactNativeHost(this) {