rfc: hovering over arguments should show argument name

Stream: lean4

[Alok Singh]

i know the argument name isn't always informative, but it usually is and ideally should be.

Say I have a function f (steps : Nat) := .. and I hover over 200 in f 200. Then it will say 200 : Nat which is certainly true, and nice to have, but some indicator that it's an argument to f in this context and that it is bound to steps would be nice