Mention how to get the basetype of an enum (#36057)

* Mention how to get the basetype of an enum
Fix #28778

* Mention Integer() instead of internal method

base/Enums.jl

@@ -106,7 +106,8 @@ end
 
 `BaseType`, which defaults to [`Int32`](@ref), must be a primitive subtype of `Integer`.
 Member values can be converted between the enum type and `BaseType`. `read` and `write`
-perform these conversions automatically.
+perform these conversions automatically. In case the enum is created with a non-default
+`BaseType`, `Integer(value1)` will return the integer `value1` with the type `BaseType`.
 
 To list all the instances of an enum use `instances`, e.g.