Feature Request: Additional expense types: transfer and income

[fabfabsto]

Hi, many thanks for your great work! I would like to run your app locally for our family but as we come from tricount I would love to have two additional expense (item) types in a group:

1. Transfers - when one member of the group is transfering money to another member. It should not add to the expenses of the group.

2. Income - that is money that the group is getting and sharing. Usually one member is receiving the money and that income should be split between the group members, not adding to the expenses of the group.

Many thanks!