issue folder name

[nbsmith]

Is your feature request related to a problem? Please describe.
A way to substitute the beginning of each downloaded issue with a customized string.

Describe the solution you'd like
Add a flag for the command line for example: -issue-folder-name="Chapter ". The issue number would appear after the custom string so you get issues like Chapter 1, Chapter 2, Chapter 3, etc.

Describe alternatives you've considered
Using a rename program or batch file or doing it manually. All seem sub-optimal.

Additional context
I already did the necessary changes on my end, tested, and have used it for a month with this change with no problems.