Let read one row with `read_rows`

[MonsieurV]

Sometimes we compute ranges (for eg. see below, chunking to read a great number of rows), and one range ends up containing only one row. In this case it is handy not to have to conditionally use read_row but just read this range of one row with read_rows.

Example of chunking where we can end up we only a range of one row:

{:ok, rows_number} = GSS.Spreadsheet.rows(sheetPid)

1..rows_number
|> Enum.chunk_every(250)
|> Enum.reduce([], fn indexes_chunk, rows ->
  start_range = List.first(indexes_chunk)
  end_range = List.last(indexes_chunk)
  Logger.info("Reading #{start_range}:#{end_range} rows from Sheet")

  {:ok, chunk_rows} =
    GSS.Spreadsheet.read_rows(
      sheetPid,
      start_range,
      end_range,
      timeout: 20000
    )

  rows ++ chunk_rows
end)

I've tested this PR in a project, seems to be working as intended.