Add ScRAT

[VladimirShitov]

• Add ScRAT to the list of single-cell transformers. This is a reasonably simple model but might be worth mentioning
• Fix a small typo

[VladimirShitov]

Thank you for your comments; I addressed them :) I'm not sure how to classify input embeddings, though. Would you consider cell embeddings followed by attention layer a "value projection"?

Regarding COMBAT, there is a link to CellXGene.

[VladimirShitov]

@szalata , could you take a look at the merge conflict? Quite a few lines changed with a recent commit in main. You know the file better, so perhaps it's faster for you to fix it :)

[szalata]

great! ofc!