add functionality to allow prioritizing horizontal chunking over temporal dimension

• this MR adds functionalities that assess Issue #1 (closed)
• it also adds a function to quickly check the chunksizes of the datasets, for a quickview.

src/rechunk_data/tests/conftest.py

 """pytest definitions to run the unittests."""
 
 from pathlib import Path
-from tempfile import TemporaryDirectory, NamedTemporaryFile
+from tempfile import NamedTemporaryFile, TemporaryDirectory
 from typing import Generator, Tuple
 
 import dask
-import pytest
 import numpy as np
+import pytest
 import xarray as xr