Bevy cannot run in the background on Android

## Bevy version

main (b61397e32bca34958e57198c0969359da647eafa) and latest release (0.11.2)

## What you did

Run the android example on a real device (Samsung Galaxy S10+). Now press the home button to minimize the app, then open it back up.

## What went wrong

The App quits (at least logs do not indicate a crash) and will start from the beginning when reopened.

## Additional information

This is a known problem (see some general discussion about life cycle handling in #86), but I couldn't find an open issue for it.

Start by running the Android example on a real device, then reproduce the behavior by minimizing and reopening it. Read the lifecycle discussion in issue #86 and compare it with the Android example's handling; done should mean the app no longer quits and restarts after returning from the background.

Written by the indexing model from the issue text.