feat: supsub

[Tabaie]

Integrate the superscript and subscript functions into gnark-crypto (superscript is useful for pretty printing of polynomials)

[gbotrel]

lgtm, maybe nitpicking; since you added that in utils package, some method will read like utils.Sub(..) which in the context of the rest of the library sounds a bit confusing :)

[Tabaie]

lgtm, maybe nitpicking; since you added that in utils package, some method will read like utils.Sub(..) which in the context of the rest of the library sounds a bit confusing :)

That's a great point. I'll change it to ToSubscript.