This Widgets tracks both the app lifecycle and the screen visibility
onStart will be called only when the Widget is displayed for the first time
(= during the initState phase)
onResume will be called once the app is reopened (eg: the app is minimized
and brought back to front)
onPause will be called once the app is minimized
onVisible will be called if this part of the tree is visible
onInvisible will be called if this part of the tree is invisible