feat(topology/algebra): uniform continuity from 0 (#7318)
From https://leanprover.zulipchat.com/#narrow/stream/217875-Is-there.20code.20for.20X.3F/topic/Linear.20map.20is.20continuous.20if.20it's.20continuous.20at.20zero/near/234714207, thanks to @PatrickMassot.
