Update link to documentation
# AWS IoT Device SDK C v4.0.0 Beta
-**[Link to API documentation](https://docs.aws.amazon.com/freertos/latest/lib-ref/html3/main/index.html)**
+**[Link to API documentation](https://docs.aws.amazon.com/freertos/latest/lib-ref/c-sdk/main/index.html)**
[![Build Status](https://travis-ci.org/aws/aws-iot-device-sdk-embedded-C.svg?branch=v4_beta)](https://travis-ci.org/aws/aws-iot-device-sdk-embedded-C)
[![Coverage Status](https://coveralls.io/repos/github/aws/aws-iot-device-sdk-embedded-C/badge.svg?branch=v4_beta)](https://coveralls.io/github/aws/aws-iot-device-sdk-embedded-C?branch=v4_beta)
