[Enhancement]: Wrong gains for weight initialization

Enhancement

The recommended gains for the weight init depend on the used activation function, see torch docs. However, as for now the used gains are statically implemented and always the same in ActorCriticPolicies. See here.

I recommend making the gains dependent on the activation function used(, i.e. probably mainly ReLU and tanh).

If you agree with this, I would like to implement it myself and PR.

Thanks and a good day!

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