feat: port Analysis.SpecialFunctions.Exp (#3988)

Author: pechersky

Mathlib.lean

@@ -421,6 +421,7 @@ import Mathlib.Analysis.NormedSpace.RieszLemma
 import Mathlib.Analysis.NormedSpace.Star.Basic
 import Mathlib.Analysis.NormedSpace.Units
 import Mathlib.Analysis.Seminorm
+import Mathlib.Analysis.SpecialFunctions.Exp
 import Mathlib.Analysis.SpecialFunctions.Polynomials
 import Mathlib.Analysis.SpecialFunctions.Trigonometric.Chebyshev
 import Mathlib.Analysis.SpecificLimits.Basic