feat: port Topology.Inseparable (#1908)

Author: urkud

Mathlib.lean

@@ -927,6 +927,7 @@ import Mathlib.Topology.Bornology.Constructions
 import Mathlib.Topology.Bornology.Hom
 import Mathlib.Topology.Constructions
 import Mathlib.Topology.ContinuousOn
+import Mathlib.Topology.Inseparable
 import Mathlib.Topology.LocalExtr
 import Mathlib.Topology.LocallyFinite
 import Mathlib.Topology.Maps