v1.2: stability tweaks

hello CEREALMAN, enjoy your STABILITY UPDATES

• fix a mac crash whenever the player dies
  • change to Godot’s “Forward+” renderer
  • I’m unsure how widespread the problem was, but this fixes the crash for the one person who reported it
  • other platforms might use less resources, now that the renderer is more modern
• load all shaders on startup
• better v1.0 save migration - easier to revert or troubleshoot if something goes wrong somehow
• change death animation