ANTEX header records. version and pcv_type are nil when the source has
no such record; comments are the header COMMENT texts in file order.
Summary
Types
@type t() :: %Sidereon.GNSS.Antex.Header{ comments: [String.t()], end_of_header: boolean(), pcv_type: Sidereon.GNSS.Antex.PcvTypeRecord.t() | nil, version: Sidereon.GNSS.Antex.Version.t() | nil }