[#258] Remove deprecated `kotlin-android-extensions` plugin

demo-app/build.gradle

@@ -1,13 +1,12 @@
 apply plugin: 'com.android.application'
 apply plugin: 'kotlin-android'
-apply plugin: 'kotlin-android-extensions'
+apply plugin: 'kotlin-parcelize'
 apply plugin: 'kotlin-kapt'
 apply plugin: 'androidx.navigation.safeargs'
 
 android {
     ndkVersion "21.1.6352462"
     compileSdkVersion 29
-    viewBinding.enabled = true
     defaultConfig {
         applicationId "cash.z.ecc.android.sdk.demoapp"
         minSdkVersion 21
@@ -16,6 +15,9 @@ android {
         versionName "1.0"
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
     }
+    buildFeatures {
+        viewBinding true
+    }
     flavorDimensions 'network'
     productFlavors {
         // would rather name them "testnet" and "mainnet" but product flavor names cannot start with the word "test"