Idea: Add storage amount/price calculator for Sia setup or add ETA for balance to run out.

[MeijeSibbel]

Some users have reported that they would like to send the amount of funds necessary for a (x) amount of storage and a (y) amount of time. The idea would be to add a setup screen where users can say input the amount of GB/TB that they want to store and then the app outputs how many Sia they have to deposit.

Alternatively we can add a pay-as-you-go estimator in either the tray menu or settings, which shows the user how much time remaining until they have to add new funds, this can be in the form of numbers or a bar below the used space bar.