chore(topology/algebra/group_with_zero): continuity attributes (#6965)
chore(topology/algebra/group_with_zero): continuity attributes (#6965)

Some `@[continuity]` tags, requested at https://github.com/leanprover-community/mathlib/pull/6937#discussion_r604139611





leanprover-community/mathlib,leanprover-community/mathlib