Make the ship invulnerable

# Description:
A god mode, makes the ship invulnerable so that it doesn't get damaged by laser fire, missiles, etc.
Another @Luomu invention.

Make the ship invulnerable by passing 1, and vulnerable again by passing 0.
`import("Game").player:SetInvulnerable(0)`
`import("Game").player:SetInvulnerable(1)`