Trello Card: https://trello.com/c/zWAyAbk4/112-add-a-field-spesenverzicht-on-the-volunteer-excel

Field is Spesenverzicht http://localhost:3000/volunteers

As a superadmin, I want to know which volunteers waive their billing expenses: -> add new field "Spesenverzicht" to volunteer excel: /views/volunteers/index.xlsx.axlsx