Markdown front matter reader and writer used by Prompt Runner packet files.
@type document() :: %{attributes: map(), body: String.t()}
@spec dump(map(), String.t()) :: String.t()
@spec load_file(String.t()) :: {:ok, document()} | {:error, term()}
@spec parse(String.t()) :: {:ok, document()} | {:error, term()}
@spec write_file(String.t(), map(), String.t()) :: :ok | {:error, term()}