✨ Add ability to store and view the balance data of a user

[JustYourBud]

Additions

• ✨ Add connection to MongoDB schema

• ✨ Add the User model

• ✨ #2

• ✨ Add getBalance() to return a user's balance data

• ✨ #3

• [x] The additons and changes made have been tested.

[jonahbedouch]

LGTM 👍🏼