Add identifier to reserved types and fix reserved_type references to use correct reference rather than ghost-type

[onno-vos-dev]

This broke the AWS-Erlang & AWS-Elixir nightly builds which went unnoticed.

Example:

%% Example:
%% quicksight_identifier() :: #{
%%   <<"Identity">> => string()
%% }
-type quicksight_identifier() :: #{binary() => any()}.

%% Example:
%% topic_sort_clause() :: #{
%%   <<"Operand">> => quicksight_identifier(),
%%   <<"SortDirection">> => list(any())
%% }
-type topic_sort_clause() :: #{binary() => any()}.

  @typedoc """

  ## Example:

      quicksight_identifier() :: %{
        "Identity" => String.t()
      }

  """
  @type quicksight_identifier() :: %{String.t() => any()}

  @typedoc """

  ## Example:

      topic_sort_clause() :: %{
        "Operand" => quicksight_identifier(),
        "SortDirection" => list(any())
      }

  """
  @type topic_sort_clause() :: %{String.t() => any()}

[onno-vos-dev]

I think this can close #114 , right?

Thank you @onno-vos-dev!

Yes it can! Somehow I missed that issue 🙈 I blame summer vacation...