Implement option to choose fiat in receive screen

[sandakersmann]

We should implement an option to choose fiat for the requested amount in the receive screen.

[surajkale07]

Hey @sandakersmann , I have a interest in this flutter project. Can you elaborate more about the issue so I can contribute in fixing this issue

[sandakersmann]

Right now you can only add a number of PPC to the QR code in the receive screen. The QR code should only contain the amount in PPC, but the UI should enable you to enter an amount in fiat as an option. This amount in fiat will then be converted to an amount in PPC for the QR code.

In the send screen you can see that we have a toggle switch to choose between PPC and fiat. We should have the same in the receive screen.

Great to have more people contributing! Would be great if you could go through the translations in the languages you speak as well :)