Fix Gradle config

Author: Correct-Syntax

android/app/build.gradle

@@ -56,14 +56,21 @@ android {
         versionName flutterVersionName
     }
 
-    buildTypes {
+    signingConfigs {
         release {
             keyAlias keystoreProperties['keyAlias']
             keyPassword keystoreProperties['keyPassword']
             storeFile keystoreProperties['storeFile'] ? file(keystoreProperties['storeFile']) : null
             storePassword keystoreProperties['storePassword']
         }
     }
+    buildTypes {
+        release {
+            minifyEnabled = true
+            shrinkResources = true
+            signingConfig signingConfigs.release
+        }
+    }
 
     dependenciesInfo {
         // Disables dependency metadata when building APKs.