Issue with MADDPG and MATD3

Hi! I am trying to use ElegantRL for multi-agent RL training as it seems very well written.

I tried to use MADDPG or MATD3. But none of these agents seem to be runnable. For example, the construction method for `AgentDDPG` requires arguments: https://github.com/AI4Finance-Foundation/ElegantRL/blob/b447f3a04993e0ab8fc11017c1b20c6d560f493b/elegantrl/agents/AgentDDPG.py#L29

But the MADDPG or MATD3 implementation doesn't provide that.
https://github.com/AI4Finance-Foundation/ElegantRL/blob/b447f3a04993e0ab8fc11017c1b20c6d560f493b/elegantrl/agents/AgentMADDPG.py#L43

There are also other places that don't seem to be compatible.

I wonder if this is a problem with the multi-agent implementations using a legacy version of the codebase. And is it possible to provide a minimal working demo for MADDPG or MATD3?

Thanks a lot!!