Expose nclasses option for DenseNet

[theabhirath]

Previously, the nclasses option was not exposed for the DenseNet API with the config option.

This PR adds that. Would be good to have a patch release too if possible (only with this commit and not the previous breaking change), since I'm trying to train some models and this will help with that 😅

[darsnack]

Instead of maintaining a separate non-breaking branch, maybe the easiest thing would be to revert the breaking conv + bn changes since they weren't a major impact to TTFG anyways. We can release the other changes along with this and keep the breaking stuff in a separate, new PR.

[theabhirath]

Instead of maintaining a separate non-breaking branch, maybe the easiest thing would be to revert the breaking conv + bn changes since they weren't a major impact to TTFG anyways. We can release the other changes along with this and keep the breaking stuff in a separate, new PR.

I've opened #155 to address this. I will run some more tests when I get time to ascertain just how much returning a Chain helps for conv_bn but for now, this should help make #151 non-breaking

[darsnack]

Can you bump the patch too?