low rank update on `cacheval`

[vpuri3]

If you're reusing a LinearCache to solve a slightly perturbed system, it would be useful to do a low-rank update on cacheval instead of recomputing the factorization? something like a sherman-morrison formula?

ref https://infoscience.epfl.ch/record/161468?ln=en https://en.wikipedia.org/wiki/Woodbury_matrix_identity

[ChrisRackauckas]

It could be. We could add it to the interface.