Update build.gradle with note to not modify

Also update example project with missing build.gradle namespace.

Author: jkasten2

OneSignalExample/Assets/Plugins/Android/OneSignalConfig.androidlib/build.gradle

@@ -1,6 +1,12 @@
+/*
+   WARNING: Do NOT Modify! Changes will be overwritten by the OneSignal plugin.
+*/
+
 apply plugin: 'com.android.library'
 
 android {
+    namespace 'com.onesignal.onesignalsdk'
+
     sourceSets {
         main {
             manifest.srcFile 'AndroidManifest.xml'
@@ -9,16 +15,16 @@ android {
 
     def unityLib = project(':unityLibrary').extensions.getByName('android')
 
-   defaultConfig {
+    defaultConfig {
         consumerProguardFiles "consumer-proguard.pro"
         minSdkVersion unityLib.defaultConfig.minSdkVersion.mApiLevel
         targetSdkVersion unityLib.defaultConfig.targetSdkVersion.mApiLevel
-   }
+    }
 
     compileSdkVersion unityLib.compileSdkVersion
     buildToolsVersion unityLib.buildToolsVersion
 
     lintOptions {
         abortOnError false
     }
-}
+}

com.onesignal.unity.android/Editor/OneSignalConfig.androidlib/build.gradle

@@ -1,3 +1,7 @@
+/*
+   WARNING: Do NOT Modify! Changes will be overwritten by the OneSignal plugin.
+*/
+
 apply plugin: 'com.android.library'
 
 android {
@@ -11,11 +15,11 @@ android {
 
     def unityLib = project(':unityLibrary').extensions.getByName('android')
 
-   defaultConfig {
+    defaultConfig {
         consumerProguardFiles "consumer-proguard.pro"
         minSdkVersion unityLib.defaultConfig.minSdkVersion.mApiLevel
         targetSdkVersion unityLib.defaultConfig.targetSdkVersion.mApiLevel
-   }
+    }
 
     compileSdkVersion unityLib.compileSdkVersion
     buildToolsVersion unityLib.buildToolsVersion