Godot 4.0 Rework

[Thane5]

I'm porting this to Godot 4.0 and cleaning some things up on the way.
Here's what still needs to be done:

• Add button Audio playback
• Make sure it can find redguardunity.exe
• Fix popup window disappearing when clicked away or file dialog opens
• (optional) Make popup window a new scene
• Disable main buttons when the options window is open
• Fix font size in options window

[Thane5]

Some more minor fixes that could be done:

• "Play Redguard" button plays not audio because launcher shuts itself down too fast
• Audio files could have a specified cooldown instead of waiting for each one to finish playing