From suggestion from Godot workflows: https://github.com/bevyengine/bevy/issues/1730#issuecomment-810321110
* Add a feature `bevy_debug` that will make Bevy read a debug config file to setup some debug systems
* Currently, only one that will exit after x frames
* Could add option to dump screen to image file once that's possible
* Add a job in CI workflow that will run a few examples using [`swiftshader`](https://github.com/google/swiftshader)
* This job takes around 13 minutes, so doesn't add to global CI duration
|example|number of frames|duration|
|-|-|-|
|`alien_cake_addict`|300|1:50|
|`breakout`|1800|0:44|
|`contributors`|1800|0:43|
|`load_gltf`|300|2:37|
|`scene`|1800|0:44|
