chore(readme): add link to official documentation

Author: mslimani

README.md

@@ -8,16 +8,75 @@ This project is an example of using Flutter with the AWS AppSync solution. It is
 
 [![Demo](https://github.com/ineat/flutter-aws-appsync-sample/blob/master/media/demo.gif)](https://github.com/ineat/flutter-aws-appsync-sample/blob/master/media/demo.mp4)
 
-### My AppSync Configuration
+AWS AppSync automatically updates web and mobile application data in real time, and offline user data is updated as soon as it is reconnected.
+If you use AppSync as a simple GraphQL API without the subscribe feature then it would be better to use the following plugin: : 
+https://pub.dartlang.org/packages/graphql_flutter
+
+
+The bridge is based on the official documentation of the AppSync SDK.
+
+AWS AppSync SDK Android : 
+https://docs.aws.amazon.com/appsync/latest/devguide/building-a-client-app-android.html
+
+AWS AppSync SDK iOS : 
+https://docs.aws.amazon.com/appsync/latest/devguide/building-a-client-app-ios.html
+
+If you want more information on the development of a flutter plugin here is an official link: https://flutter.io/developing-packages/
+
+To make this example work, AppSync is configured with the following GraphQL schema : 
+
+
+## GraphQL schema
+
+The GraphQL schema: 
+
+```graphql
+type Message {
+	id: ID!
+	content: String!
+	sender: String!
+	conversationId: Int!
+}
+
+type Mutation {
+	newMessage(content: String!, sender: String!, conversationId: Int!): Message
+}
+
+type Query {
+	getMessages: [Message]
+}
+
+type Subscription {
+	subscribeToNewMessage(conversationId: Int!): Message
+		@aws_subscribe(mutations: ["newMessage"])
+}
+
+schema {
+	query: Query
+	mutation: Mutation
+}
+```
+
+Pour créer votre schéma GraphQL pour AppSync, consulter le lien https://docs.aws.amazon.com/appsync/latest/devguide/graphql-overview.html 
+
+## Security
+
+AppSync will be secured by API Key.
+
+https://docs.aws.amazon.com/appsync/latest/devguide/security.html
+
+## Data Source
+
+The Data Source used by AppSync is a lambda. Here is this example here is a simplified version :
 
-**Lambda called by AppSync :** 
 ```javascript
 
 var incrementId = 0;
 var messages = [];
 
 exports.handler = async (event, context, callback) => {
     switch (event.field) {
+        // match with Data Template resolver
         case 'getMessages':
             getMessages(event, context, callback);
             break;
@@ -46,40 +105,12 @@ async function newMessage(event, context, callback) {
 }
 ```
 
-**Schema GraphQL in App Sync :** 
-
-```graphql
-type Message {
-	id: ID!
-	content: String!
-	sender: String!
-	conversationId: Int!
-}
-
-type Mutation {
-	newMessage(content: String!, sender: String!, conversationId: Int!): Message
-}
+To link the GraphQL schema methods to the lambda refer to the following link : https://docs.aws.amazon.com/appsync/latest/devguide/tutorial-lambda-resolvers.html
 
-type Query {
-	getMessages: [Message]
-}
-
-type Subscription {
-	subscribeToNewMessage(conversationId: Int!): Message
-		@aws_subscribe(mutations: ["newMessage"])
-}
-
-schema {
-	query: Query
-	mutation: Mutation
-}
-```
-
-Settings Authorization type is : **API key**
-
-Add **resolver** into query, mutation. The data source name  is linked with the previously lambda.
+## Resolvers
 
 Request template resolver for NewMessage Mutation :
+
 ```javascript
 {
     "version" : "2017-02-28",
@@ -92,6 +123,7 @@ Request template resolver for NewMessage Mutation :
 ```
 
 Request template resolver for GetMessages Query :
+
 ```javascript
 {
     "version" : "2017-02-28",
@@ -103,13 +135,20 @@ Request template resolver for GetMessages Query :
 }
 ```
 
-Add AppSync API URL, and API Key in the file /lib/constants.dart
+## Configuration sample
+
+To configure AppSync in the project, modify the constants of the file /lib/constants.dart
+
+```dart
+const AWS_APP_SYNC_ENDPOINT = "YOUR ENDPOINT"; // like https://xxx.appsync-api.eu-central-1.amazonaws.com/graphql
+const AWS_APP_SYNC_KEY = "YOUR API KEY";
+```
 
 # Custom Configuration in your project
 
 ## 1. Android
 
-Step 1: add aws android SDK classpath
+**_Step 1:_** add aws android SDK classpath
 
 
 ```groovy
@@ -124,7 +163,7 @@ buildscript {
 
 ```
 
-Step 2: Plugin plugin and SDK
+_**Step 2:**_ Plugin plugin and SDK
 
 ```groovy
 // android/app/build.gradle
@@ -139,15 +178,16 @@ dependencies {
 }
 ```
 
-Step 3: add schema and request GraphQL
+_**Step 3:**_ add schema and request GraphQL
 
 Copy your files in :
 
 /android/app/src/main/graphql/your.package.name/*.graphql
 /android/app/src/main/graphql/your.package.name/*.json
 
 
-Step 4: Configure Android Manifest
+_**Step 4:**_ Configure Android Manifest
+
 ```xml
 
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
@@ -166,7 +206,8 @@ Step 4: Configure Android Manifest
 
 </manifest>
 ```
-Step 5: Generation GraphQL models
+
+_**Step 5:**_ Generation GraphQL models
 
 Launch gradle command : 
 
@@ -177,7 +218,7 @@ Launch gradle command :
 
 ## 2. iOS
 
-Step 1: add AWS SDK in your Podfile
+_**Step 1:**_ add AWS SDK in your Podfile
 
 ```ruby
 target 'Runner' do
@@ -186,14 +227,15 @@ target 'Runner' do
 end
 ```
 
-Step 2: Retrieve all dependencies
+_**Step 2:**_ Retrieve all dependencies
+
 ```ruby
 pod install
 ```
 
-Caution: Configure your deployment target at 9.0 (Runner.xcworkspace)
+_Caution:_ Configure your deployment target at 9.0 (Runner.xcworkspace)
 
-Step 3: add schema and request GraphQL
+_**Step 3:**_ add schema and request GraphQL
 
 Copy your files in :