Need to update documentation

FinRL_StockTrading_NeurIPS_2018 doesn't exist for example.
Also a step by step setup demo would be great.

Locate the documentation references to FinRL_StockTrading_NeurIPS_2018 and review the current setup instructions. Confirm whether that example exists, then document a working step-by-step setup demo. Done means the example reference is accurate and a newcomer can follow the setup steps.

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