Add reccuring emission background task

[PierreBresson]

• [ ] pressing Add emission button should schedule adding emission in the background according to user input, see #254
• [x] recurring emissions should also be in redux store in order to display them in emissions screen as "parent emission" of the several "normal" emissions that will appear in the month subsection. For this, create a new recurringEmission folder inside app>ducks

I have done some research on how to do it, might help :

• Expo way : https://docs.expo.io/versions/latest/sdk/task-manager/
• If we can use native in future expo releases : https://github.com/jamesisaac/react-native-background-task