[Feature Request] - Relative Attributing Propagation

Hi everybody,

I am an enthusiast user of this library, but I found an interesting generalization of LRP-alpha-beta (Relative Attributing Propagation) that would be interesting to be supported by iNNvestigate.

https://github.com/wjNam/Relative_Attributing_Propagation

The implementation is in pytorch, but maybe it would not be too difficult to port it to the iNNvestigate framework. It would be very useful and it will make the library richer.
I would try to do it myself but I am still not too practical with the framework...

What do you think about it?
PS: Thanks again for this amazing library!!