Added note for AWSAppSyncClient (#4611)

I had some trouble to get server side rendering with the AWSAppSyncClient working. I finally found a solution in awslabs/aws-mobile-appsync-sdk-js#82 but it might be worth to share it here as well. Instead of adding a big code block to each file I'll just refer to this Pull Request.

______

In case you want to use the `AWSAppSyncClient` you just need to replace the `create()` function with this function:
```jsx
import AWSAppSyncClient from 'aws-appsync';
import { AUTH_TYPE } from 'aws-appsync/lib/link/auth-link';

function create(initialState) {
  const client = new AWSAppSyncClient({
    url: AWS_AppSync.graphqlEndpoint,
    region: AWS_AppSync.region,
    auth: {
      type: AUTH_TYPE.API_KEY,
      apiKey: AWS_AppSync.apiKey,

      // Amazon Cognito Federated Identities using AWS Amplify
      //credentials: () => Auth.currentCredentials(),

      // Amazon Cognito user pools using AWS Amplify
      // type: AUTH_TYPE.AMAZON_COGNITO_USER_POOLS,
      // jwtToken: async () => (await Auth.currentSession()).getIdToken().getJwtToken(),
    },
    disableOffline: true,
  }, {
    cache: new InMemoryCache().restore(initialState || {}),
    ssrMode: true
  });

  return client;
}
```

Author: Skaronator

examples/with-apollo-and-redux-saga/lib/initApollo.js

@@ -11,6 +11,7 @@ if (!process.browser) {
 }
 
 function create(initialState) {
+  // Check out https://github.com/zeit/next.js/pull/4611 if you want to use the AWSAppSyncClient
   return new ApolloClient({
     connectToDevTools: process.browser,
     ssrMode: !process.browser, // Disables forceFetch on the server (so queries are only run once)

examples/with-apollo-and-redux/lib/initApollo.js

@@ -11,6 +11,7 @@ if (!process.browser) {
 }
 
 function create(initialState) {
+  // Check out https://github.com/zeit/next.js/pull/4611 if you want to use the AWSAppSyncClient
   return new ApolloClient({
     connectToDevTools: process.browser,
     ssrMode: !process.browser, // Disables forceFetch on the server (so queries are only run once)
@@ -35,4 +36,4 @@ export default function initApollo(initialState) {
   }
 
   return apolloClient
-}
+}

examples/with-apollo-auth/lib/initApollo.js

@@ -26,6 +26,7 @@ function create (initialState, { getToken }) {
     }
   })
 
+  // Check out https://github.com/zeit/next.js/pull/4611 if you want to use the AWSAppSyncClient
   return new ApolloClient({
     connectToDevTools: process.browser,
     ssrMode: !process.browser, // Disables forceFetch on the server (so queries are only run once)

examples/with-apollo/lib/init-apollo.js

@@ -11,6 +11,7 @@ if (!process.browser) {
 }
 
 function create(initialState) {
+  // Check out https://github.com/zeit/next.js/pull/4611 if you want to use the AWSAppSyncClient
   return new ApolloClient({
     connectToDevTools: process.browser,
     ssrMode: !process.browser, // Disables forceFetch on the server (so queries are only run once)