Private use tags. They begin with an x-, can be 1 to 8 character long, and can be freely defined and used without any registration.
Convert the tag to its String representation.
Create a PrivateUse from its components.
Fails if the list is empty or any of the components are outside the expected size (1 to 8 characters).
The x- is added automatically by toCodeString.
fromStrings [ "whatever" ] |> Maybe.map toCodeString
--> Just "x-whatever"
fromStrings [ "x", "whatever" ] |> Maybe.map toCodeString
--> Just "x-x-whatever"
fromStrings []
--> Nothing
fromStrings [ "thisistoolong" ]
--> Nothing