Add support for ESM

[tijeco]

It seems like esm could be supported in the same way as protBert is from hugging face.

berteome.unmasker(), would have to be updated, since it borrows from hugging face but would need to be tweeked to give output from ESM.

Also ESM handles masks differently ( instead of [MASK], I don't think spaces matter as much either, so it would be a bit different. Anyway, I think it would be interesting to see how the two models compare.