build_directory_md.py is not working correctly

[jai-dewani]

The script should start all the headings with ##
but it is starting every line a *

[cclauss]

Both ## and * are valid markdown.

[jai-dewani]

But ## should be used for emphasizing the folders

[jai-dewani]

#1161
It was minor bug in md_prefix(i), fixed the same.

[cclauss]

I like ## more because it create a link to a specific set of algorithms: digital-image-processing
https://github.com/TheAlgorithms/Python/blob/master/DIRECTORY.md#digital-image-processing

[jai-dewani]

Yes I am supporting the same point, the problem is that script when run is marking the folders with * instead of #