Add backoffAlgorithm to table of contents in README
* [AWS IoT Device Shadow](#aws-iot-device-shadow)
* [AWS IoT Jobs](#aws-iot-jobs)
* [AWS IoT Device Defender](#aws-iot-device-defender)
+ * [backoffAlgorithm](#backoffalgorithm)
* [AWS Collection of Metrics](#aws-collection-of-metrics)
* [Versioning](#versioning)
* [Releases](#releases)
