add piggybank feature

Feature for users where they can set up a certain saving goal

Once the goal is set up, the user can spend towards that goal

Example: user wants to save up for a laptop

1) user sets saving goal of $1000 (example price for laptop)

2) each month the user is able to “spend” towards that saving goal

3) goal is reached after a few months and now user knows they can buy the laptop responsibly & has a track record of each saving action within the app