refactor(ES.FX): convert IsExact property to method in ValueRange

- Changed the `IsExact` property in the `ValueRange` class to a method. This change improves readability and consistency with other similar functionalities.

src/ES.FX/Primitives/ValueRange.cs

@@ -22,7 +22,7 @@ public ValueRange(T min, T max)
     public T Min { get; init; }
     public T Max { get; init; }
 
-    public bool IsExact => Min.CompareTo(Max) == 0;
+    public bool IsExact() => Min.CompareTo(Max) == 0;
 
     public bool IsInRange(T value) => value.CompareTo(Min) >= 0 && value.CompareTo(Max) <= 0;