mathlib

6efec6bb - feat(topology/continuous_function): some lemmas spun off from #18392 (#18465)

feat(topology/continuous_function): some lemmas spun off from #18392 (#18465) A few miscellaneous lemmas about continuous functions needed for my Poisson summation project. Companion mathlib4 PR (blank for now) at [#2369](https://github.com/leanprover-community/mathlib4/pull/2369).