[DISC-117] Adding travelguides command (#187)

* initial travelguide add subcommand

* fixing formatting

* fixing syntax error

* added get function

* linting

* completed travelguide command

* linting

* adding deletion confirmation

* linting

* migrating travelguide.json to postgres

* linting

* linting

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Co-authored-by: Jessica Xu <jessica.xu3@student.unsw.edu.au>

Author: chlowoee