Add IBM speculator models?

[njhill]

Thanks for this nice work!

We have found that these outperform the other techniques: https://arxiv.org/abs/2404.19124

Some trained speculator models can be found here:

• https://huggingface.co/ibm-fms
• https://huggingface.co/collections/ibm-granite/granite-speculators-664b97a44ddc5640e8cd73ac