Merge branch 'readme_update_with_gpu_cache_sok' into 'master'

Update README.md

See merge request dl/hugectr/hugectr!457

Author: zehuanw2

README.md

@@ -11,6 +11,7 @@ Design Goals:
 ## Table of Contents
 * [Core Features](#core-features)
 * [Getting Started](#getting-started)
+* [HugeCTR SDK](#hugectr-sdk)
 * [Support and Feedback](#support-and-feedback)
 * [Contribute to HugeCTR](#contribute-to-hugectr)
 
@@ -148,6 +149,11 @@ If you'd like to quickly train a model using the Python interface, follow these
 
 For additional information, see the [HugeCTR User Guide](docs/hugectr_user_guide.md).
 
+## HugeCTR SDK ##
+To support the users who cannot use HugeCTR directly, we exports several important components in HugeCTR to external developers as SDK.
+* [Sparse Operation Kit](sparse_operation_kit): a python package wrapped GPU accelerated operations dedicated for sparse training / inference cases.
+* [GPU Embedding Cache](gpu_cache): a embedding cache on GPU memory designed for CTR inference workload
+
 ## Support and Feedback ##
 If you encounter any issues and/or have questions, please file an issue [here](https://github.com/NVIDIA/HugeCTR/issues) so that we can provide you with the necessary resolutions and answers. To further advance the Merlin/HugeCTR Roadmap, we encourage you to share all the details regarding your recommender system pipeline using this [survey](https://developer.nvidia.com/merlin-devzone-survey).