feat(algebraic_geometry/structure_sheaf): stalk_iso (#4047)
Given a ring `R` and a prime ideal `p`, construct an isomorphism of rings between the stalk of the structure sheaf of `R` at `p` and the localization of `R` at `p`.
Co-authored-by: Scott Morrison <scott.morrison@gmail.com>
Co-authored-by: Johan Commelin <johan@commelin.net>
