Suggestion: Separate external libraries from autograder

[geshuming]

I am proposing that external libraries are stored in a separate repository so that testing on the external libraries can be done separately and not in this repo.

Suggestion: Add feature to automatically pull/read from external library repository

• Allows for addition / removal of arbitrary number of libraries
• Separate testing of libraries from autograder

[martin-henz]

@geshuming can you compare this Issue with
source-academy/modules#2

Is there anything in your Issue that is not in mine?