Create signal "gameover" in the Spaceship scene

[davcri]

We want to add gameover mechnic to the game when the player runs out of lives.

In the spaceship scene:

• Add a gameover signal
• Dispatch the signal when the spaceship finishes its lives

We will handle the gameover screen and the spaceship destruction in another issue.

[rubin0]

Doing this

[rubin0]

While I was reading the code, I found out this feature exists already.

HUD script lines 3 and 43

[davcri]

Thanks @Karbb! Closing this!