chore: android version

Author: funnyzak

android/app/build.gradle

@@ -134,8 +134,8 @@ android {
         applicationId "github.funnyzak.v2ex"
         minSdkVersion rootProject.ext.minSdkVersion
         targetSdkVersion rootProject.ext.targetSdkVersion
-        versionCode 20
-        versionName "0.5.6"
+        versionCode 21
+        versionName "0.5.7"
     }
     splits {
         abi {