Provide an Example for Inference

[FrankLeeeee]

Need to provide an example of doing inference, this should be synced in the documentation as well.

[binmakeswell]

The feature depends on https://github.com/hpcaitech/ColossalAI/issues/256

[GongZhengLi]

I recommend you to use the Easy and Efficient Transformer(EET) for inference.