`$0` is a helpful variable in other browsers' JS consoles, which points
to whichever DOM Node is currently selected in the DOM Inspector. And
now we have it too! :^)
ConsoleGlobalObject is used as the global object when running javascript
from the Browser console. This lets us implement console-only functions
and variables (like `$0`) without exposing them to webpage content. It
passes other calls over to the usual WindowObject so any code that would
have worked in the webpage will still work in the console. :^)
