restrict wsi_dir.glob to files

[xalexalex]

fixes #189

this could also be done differently, e.g. glob("*") or iterdir + checking if is_dir

[kaczmarj]

thanks @xalexalex for your contribution! instead of globbing with .* to get files, could we use a combination of iterdir and is_file()? for example, my concern is that this might capture hidden files. and while unlikely, it's possible that a file might not have an extension and therefore no . character.

i am thinking of something like this:

from pathlib import Path
files_in_wsi_dir =[p for p in wsi_dir.iterdir() if p.is_file()]

thanks for bringing up the MRXS use case!

[kaczmarj]

thanks @xalexalex for the contribution!