Add shadow repo link to README (#1891)

Author: gregbreen

README.md

@@ -115,7 +115,7 @@ See memory requirements for the latest release [here](https://aws.github.io/aws-
 
 #### AWS IoT Device Shadow
 
-The AWS IoT Device Shadow library enables you to store and retrieve the current state one or more shadows of every registered device. A device’s shadow is a persistent, virtual representation of your device that you can interact with from AWS IoT Core even if the device is offline. The device state is captured in its "shadow" is represented as a [JSON](https://www.json.org/) document. The device can send commands over MQTT to get, update and delete its latest state as well as receive notifications over MQTT about changes in its state. The device’s shadow(s) are uniquely identified by the name of the corresponding "thing", a representation of a specific device or logical entity on the AWS Cloud. See [Managing Devices with AWS IoT](https://docs.aws.amazon.com/iot/latest/developerguide/iot-thing-management.html) for more information on IoT "thing". This library supports named shadows, a feature of the AWS IoT Device Shadow service that allows you to create multiple shadows for a single IoT device. More details about AWS IoT Device Shadow can be found in [AWS IoT documentation](https://docs.aws.amazon.com/iot/latest/developerguide/iot-device-shadows.html).
+The [AWS IoT Device Shadow](https://github.com/aws/device-shadow-for-aws-iot-embedded-sdk) library enables you to store and retrieve the current state one or more shadows of every registered device. A device’s shadow is a persistent, virtual representation of your device that you can interact with from AWS IoT Core even if the device is offline. The device state is captured in its "shadow" is represented as a [JSON](https://www.json.org/) document. The device can send commands over MQTT to get, update and delete its latest state as well as receive notifications over MQTT about changes in its state. The device’s shadow(s) are uniquely identified by the name of the corresponding "thing", a representation of a specific device or logical entity on the AWS Cloud. See [Managing Devices with AWS IoT](https://docs.aws.amazon.com/iot/latest/developerguide/iot-thing-management.html) for more information on IoT "thing". This library supports named shadows, a feature of the AWS IoT Device Shadow service that allows you to create multiple shadows for a single IoT device. More details about AWS IoT Device Shadow can be found in [AWS IoT documentation](https://docs.aws.amazon.com/iot/latest/developerguide/iot-device-shadows.html).
 
 The AWS IoT Device Shadow library has no dependencies on additional libraries other than the standard C library. It also doesn’t have any platform dependencies, such as threading or synchronization. It can be used with any MQTT library and any JSON library (see [demos](demos/shadow) with coreMQTT and coreJSON).