reduce app size

Author: dongyuwei

android/app/build.gradle

@@ -90,12 +90,12 @@ apply from: "../../node_modules/react-native/react.gradle"
  * Upload all the APKs to the Play Store and people will download
  * the correct one based on the CPU architecture of their device.
  */
-def enableSeparateBuildPerCPUArchitecture = false
+def enableSeparateBuildPerCPUArchitecture = true
 
 /**
  * Run Proguard to shrink the Java bytecode in release builds.
  */
-def enableProguardInReleaseBuilds = false
+def enableProguardInReleaseBuilds = true
 
 /**
  * The preferred build flavor of JavaScriptCore.
@@ -159,6 +159,7 @@ android {
             // see https://facebook.github.io/react-native/docs/signed-apk-android.
             signingConfig signingConfigs.debug
             minifyEnabled enableProguardInReleaseBuilds
+            shrinkResources true
             proguardFiles getDefaultProguardFile("proguard-android.txt"), "proguard-rules.pro"
         }
     }