Lack of a `bias` option

[EIFY]

Hi, I just noticed that the Linear module doesn't have an option for a learnable additive bias, though adding it is quite straightforward. Is there a reason for the lack of it?

[EIFY]

(Conceptually I think adding a learnable bias is the same as adding the embedding of a constant (say zero) in this framework but I don't know if that will work well in practice)

[EIFY]

I went ahead and implemented one as part of simple ViT (linear head variant of https://arxiv.org/abs/2205.01580):
#10