Missing type annotation for sigmoid_binary_cross_entropy

[blackblitz]

In the losses, only sigmoid_binary_cross_entropy is missing type annotations, which may cause type checkers to miss type errors. This is also reflected in the documentation. Could it be type-annotated?

[ismailtrm]

Hey! I’d like to work on this. I can add the type annotations to sigmoid_binary_cross_entropy following the same pattern as the other loss functions like hinge_loss.

I’ll get the tests running locally and make sure everything passes before opening the PR.