Firebase example update

[arthuro555]

It seems the firebase example has been broken for... a year and a half? When I added queries to GDevelop, I updated the example to use the new features, and reconfigured the backend for this, but it seems like I must've forgotten to upload the new example version, but the old version cannot be used with the new backend security rules and config...

Here is the file I had on my PC from a year and a half ago, I only changed the "Authentication" scene to use the new button object and text input, since the old text inputs did not seem to work anymore when previewing from the PC version of GDevelop (although the web version ran fine???). I frankly don't remember if it was completed, so proper testing and reviewing may be needed. There is definitely room for much more improvement, but I don't have the time, energy or willpower to work on this example anymore, so I'm only submitting what is needed to keep it in a functional condition.

FirebaseExample.zip