The visibility of the toolbar can be toggled by interacting with the main screen.
This change allows the toolbar to be configured to be 'always visible'. This voids
the 'toggle' functionality.

Turns out React Native offers an object with the following definition:

{
    bottom: 0,
    left: 0,
    position: 'absolute',
    right: 0,
    top: 0
}

Wait until the right button size has been calculated before rendering it.

- add 10px of padding on the sizes of the toolbar
- make the button margin smaller (from 10 to 7)
- increate the secondary button factor to 85%, thus rising the maximum secondary
  button size to 50 (from the previous 48)

- 5 buttons in the (now single) toolbar
- Overflow menu in the form of a BottomSheet
- Filmstrip on the right when in wide mode

Contributing all buttons in one place goes against the designs that we
set out at the beginning of the project's rewrite and that multiple of
us have been following since then.