mathlib3

0f4d823c - feat(topology/algebra/uniform_ring): ring completions and algebra structures (#14841)

feat(topology/algebra/uniform_ring): ring completions and algebra structures (#14841) If `A` is an algebra over a commutative ring `R`, so is the `uniform_space.completion` of `A`. If `A` is a normed algebra over a normed field `𝕜`, then so is `uniform_space.completion A`. Co-authored-by: Eric Wieser <wieser.eric@gmail.com>