Adding type hints for Distilbert
# What does this PR do?

Added type hints for DistillBert


Fixes # (https://github.com/huggingface/transformers/issues/16059)

There are some slight issues re the type signatures, eg the example below where the code will fail if the head_mask paramerter is actually none, however I didn't remove the default paramerter as that would require a change in parameter order etc.

(https://github.com/johnryan465/transformers/blob/a11858c3dd7e28dec615c2d00112267ed231c657/src/transformers/models/distilbert/modeling_distilbert.py#L318) 

@Rocketknight1 

_The documentation is not available anymore as the PR was closed or merged._<|||||>@johnryan465 I reviewed things and you're right - `Tuple[torch.Tensor, ...]` is correct! Let me know when you're happy with the rest and I'll do another review and hopefully merge.<|||||>@Rocketknight1  I have gone through your comments and I hopefully addressed them. I'm happy enough with the code now I think. Have a good St. Patrick's Day weekend ☘️!<|||||>It looks perfect now, thank you! :shamrock: 