Add Mobile Hub section (#588)

* Added Mobile Hub section.

* Fixed formatting, some rewording.

* More wordsmithing.

README.md

@@ -59,6 +59,7 @@ Table of Contents
 | [Kinesis Streams](#kinesis-streams) | [📗](#kinesis-streams-basics) | [📘](#kinesis-streams-tips) | [📙](#kinesis-streams-gotchas-and-limitations) |
 | [Kinesis Firehose](#kinesis-firehose) |  |  | [📙](#kinesis-firehose-gotchas-and-limitations) |
 | [Device Farm](#device-farm) | [📗](#device-farm-basics) | [📘](#device-farm-tips) | [📙](#device-farm-gotchas-and-limitations) |
+| [Mobile Hub](#mobile-hub) | [📗](#mobile-hub-basics) | [📘](#mobile-hub-tips) | [📙](#mobile-hub-gotchas-and-limitations) |
 | [IoT](#iot) | [📗](#iot-basics) | [📘](#iot-tips) | [📙](#iot-gotchas-and-limitations) |
 | [SES](#ses) | [📗](#ses-basics) | [📘](#ses-tips) | [📙](#ses-gotchas-and-limitations) |
 | [Certificate Manager](#certificate-manager) | [📗](#certificate-manager-basics) | [📘](#certificate-manager-tips) | [📙](#certificate-manager-gotchas-and-limitations) |
@@ -1831,6 +1832,27 @@ Device Farm
 - 🔸AWS provide several tools and plugins for Device Farm, however, it doesn‘t cover all cases or platforms. It may require developing specific tools or plugins to support specific requirements.
 - ❗In general, Device Farm doesn‘t have Android devices from Chinese companies like Huawei, Meizu, Lenovo, etc. An actual list of supported devices located [here](https://aws.amazon.com/device-farm/device-list/).
 
+Mobile Hub
+----------
+
+### Mobile Hub Basics
+
+* 📒 [Homepage](https://aws.amazon.com/mobile/) ∙ [User guide](https://docs.aws.amazon.com/mobile-hub/latest/developerguide/) ∙ [FAQ](https://aws.amazon.com/mobile/faqs/) ∙ [Pricing](https://aws.amazon.com/mobile/pricing/)
+- **Mobile Hub** orchestrates multiple services to create an AWS backend for mobile and web applications.
+- Each _project_ in Mobile Hub has one _backend_ made up of configurable features, plus one or more _applications_.
+ - Features include Analytics, Cloud Logic, Conversational Bots, Hosting and Streaming, NoSQL Database, User Data Storage and User Sign-In. Each feature uses one or two services to deliver a chunk of functionality.
+ - Services used include [API Gateway](#api-gateway), [CloudFront](#cloudfront), Cognito, [Device Farm](#device-farm), [DynamoDB](#dynamodb), [Lambda](#lambda), Lex, Pinpoint and [S3](#S3).
+ - Application SDKs exist for Android (Java), iOS (Swift), Web (JS) and React Native (JS). There is also a CLI for JavaScript applications.
+
+### Mobile Hub Tips
+- The Mobile Hub [console](https://console.aws.amazon.com/mobilehub/home#/) has starter kits and tutorials for various app platforms.
+- The CLI allows local development of Lambda code (JS by default) with `awsmobile {pull|push}` commands, to sync from cloud to folder, and back again.
+- Mobile Hub itself is free, but each of the services has its own pricing model.
+
+### Mobile Hub Gotchas and Limitations
+- 🔸The Cloud API feature allows importing an existing Lambda function instead of defining a new one, but there are some rough edges with the CLI. Check the GitHub [issues](https://github.com/aws/awsmobile-cli/issues).
+- ❗Mobile Hub uses CloudFormation under the covers, and gets confused when a service is changed outside of the Mobile Hub console.
+
 IoT
 ---