Implement hands on hp-add-tags

[izruff]

Exercise Review

Exercise Discussion

#92

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]

This is pending comments from @damithc on the original hands-on discussion, but we might not need to fork the repository.