Test that latitude & longitude coordinates for a new dataset are for pixel centers (not corners)

[JackKelly]

(This issue is spun out of a discussion on PR 184)

To quote Alden:

if [the pixel coordinates] match what you get from xr.load_dataset(ICON_EU_GRIB_FILENAME_FROM_DWD, engine='cfgrib') they are centers. Another way to confirm is the dataset bounds in gdalinfo should be 0.0625 / 2 wider than the min/max values here.

Perhaps these tests should be implemented as a test in src/reformatters/example/template_config_test.py.

[aldenks]

one way to do this with the existing dependencies i think is with rasterio:

1. use rasterio to get the bounds of a file min_x, min_y, max_x, max_y = reader.bounds
2. pixel_size_x, pixel_size_y = reader.transform.a, reader.transform.e
3. assert min_x + (pixel_size_x / 2) == template_ds["x_coord"].min()

(i haven't checked this or i would have put it in a PR :) )