Simple method to export user data as json/csv

[peterschussheim]

Thanks to all contributors to this package.

I'd like to export leetcode data to a local file, format is not really important to me, all I want is some option to generate a file with all questions and as much info about each question as possible (most likely something similar to the output of leetcode list -x).

What i'd like to do with the data is maintain a minimal spreadsheet where I can record and view my progress according to different criteria, such as "show all questions I've completed that are tagged with 'linked-list" and "fast, slow pointer".

What would be the minimal change to provide this feature? I'd be happy to send a pull request.