Implement hands on hp-add-remote

[VikramGoyal23]

Exercise Review

Exercise Discussion

#55

Checklist

• If you require a new remote repository on the Git-Mastery organization, have you created a request for it?
• Have you written unit tests using repo-smith to validate the exercise grading scheme?
• Have you tested the download script using test-download.sh?
• Have you verified that this exercise does not already exist or is not currently in review?
• Did you introduce a new grading mechanism that should belong to git-autograder?
• Did you introduce a new dependency that should belong to app?

[woojiahao]

LGTM! Let's wait a little bit to confirm with @damithc on the follow-up steps since we're looking at this for the winter internship!