Add new book on R Torch

[cderv]

https://skeydan.github.io/Deep-Learning-and-Scientific-Computing-with-R-torch/

But this is a Quarto Book... not sure we should / could list them.

@yihui do you think we should update our homepage to support also some Quarto Book ?

[yihui]

I don't have an opinion. You can make the decision.

[cderv]

Ok. I'll try to evaluate what that entails because I think we retrieve some informations of the online books even for pinned one, so it probably requires an evoluation in the code.