`/import` command to speed up initializing the challenges

[KNOXDEV]

Document and implement a new command that takes in a CSV file of Challenges, and generates the corresponding Categories and Challenges in the CTF, populating all the necessary fields:

name, author, points, flag, description, etc.

The CSV file provided will be parsed and MERGED with existing challenges (challenges with the same name will be overridden by the spreadsheet).

[KNOXDEV]

This is mostly done for now, we still need to do points and flags manually but we can tackle that later