Added the solution for Grouping people by city

[karthikunifytech]

• Added src/karthik/group-people-data/groupPeopleData.ts which contains solutions for grouping people by city
• Added src/karthik/group-people-data/data.ts which contains the initial data
• The file src/karthik/group-people-data/groupPeopleData.ts contains 1 function - groupPeopleByCity
• Added src/karthik/group-people-data/groupPeopleData.spec.ts for unit tests for the function - groupPeopleByCity
• The file src/karthik/narcissisticNumbers/groupPeopleData.spec.ts contains 1 test suite and 5 test cases.

[krajasekhar-unify]

Good logic. Please check if the comments shall be considered. Also please link the pull request to the original issue in the Linked Issues section.

Please link the PR to the original issue. Else tracking would be difficult.