refactor: recreate ios, android, web and macOS folders for example app (

#8255)

Co-authored-by: pr_Mais <hiimechi@gmail.com>
Co-authored-by: Mike Diarmid <mike.diarmid@gmail.com>

packages/cloud_firestore/cloud_firestore/example/.metadata

@@ -0,0 +1,10 @@
+# This file tracks properties of this Flutter project.
+# Used by Flutter tool to assess capabilities and perform upgrades etc.
+#
+# This file should be version controlled and should not be manually edited.
+
+version:
+  revision: 7e9793dee1b85a243edd0e06cb1658e98b077561
+  channel: stable
+
+project_type: app

packages/cloud_firestore/cloud_firestore/example/android/.gitignore

@@ -0,0 +1,13 @@
+gradle-wrapper.jar
+/.gradle
+/captures/
+/gradlew
+/gradlew.bat
+/local.properties
+GeneratedPluginRegistrant.java
+
+# Remember to never publicly share your keystore.
+# See https://flutter.dev/docs/deployment/android#reference-the-keystore-from-the-app
+key.properties
+**/*.keystore
+**/*.jks

packages/cloud_firestore/cloud_firestore/example/android/app/build.gradle

@@ -22,22 +22,32 @@ if (flutterVersionName == null) {
 }
 
 apply plugin: 'com.android.application'
+apply plugin: 'kotlin-android'
 apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
 
 android {
-    compileSdkVersion 31
+    compileSdkVersion flutter.compileSdkVersion
 
-    lintOptions {
-        disable 'InvalidPackage'
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
+    }
+
+    kotlinOptions {
+        jvmTarget = '1.8'
+    }
+
+    sourceSets {
+        main.java.srcDirs += 'src/main/kotlin'
     }
 
     defaultConfig {
-        applicationId 'io.flutter.plugins.firebase.firestoreexample'
+        // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
+        applicationId "io.flutter.plugins.firebase.firestoreexample"
         minSdkVersion 19
-        targetSdkVersion 31
+        targetSdkVersion flutter.targetSdkVersion
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName
-        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
         multiDexEnabled true
     }
 
@@ -55,8 +65,5 @@ flutter {
 }
 
 dependencies {
-    testImplementation 'junit:junit:4.13.2'
-    androidTestImplementation 'androidx.test:runner:1.4.0'
-    androidTestImplementation 'androidx.test:rules:1.4.0'
-    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
+    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
 }