Sub Terra Draconis, now for Linux

Sub Terra Draconis is now available for Linux. This has been tested on Ubuntu 22, and it will most likely run on any recent or semi-recent distro that supports the Allegro library.

Aside from that, this patch includes bugfixes as follows,

• Added voice narration for the story screens.
  
• Fixed file interactions in level editor and Steam workshop.
  
• Fixed bug ending on the wrong map screen, and adding hotkeys for map switching.
  
• Fixed game hanging after incorrect keypress.
  
• Fixed accented letters in German.