About adding KGCN as an example of Recommender Systems

## 🚀 Feature
Can kgcn be used as an example of a recommendation system?
Examples of recommendation systems are few.
KGCN involves neighbor sampling, which is a good example of Nodeflow.
It's also not too complicated
Hope to implement with Pytorch.

(www19)Knowledge Graph Convolutional Networks for Recommender Systems
[https://arxiv.org/abs/1904.12575](url)
[https://github.com/hwwang55/KGCN](url)