✨ building workflow

Author: niuhuan

android/app/build.gradle

@@ -47,7 +47,7 @@ android {
         applicationId "opensource.wax"
         // You can update the following values to match your application needs.
         // For more information, see: https://docs.flutter.dev/deployment/android#reviewing-the-gradle-build-configuration.
-        minSdkVersion 19 // flutter.minSdkVersion
+        minSdkVersion 21 // flutter.minSdkVersion
         targetSdkVersion flutter.targetSdkVersion
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName