fix: remove Hardcore mode, disable Elytra by default, add bug tracker

- Remove HardcoreMode (lose all rewards on fall)
- Disable Elytra mode in default config
- Add todo.md with 20 identified bugs
- Fix 3 remaining bugs: checkPlayerFall continue, removeTrailBlocks sync, scoredBlocks clear on fall

src/main/resources/locales/en.yml

@@ -40,11 +40,6 @@ play:
       name: "&#00D4FF&lGravity Shift"
       lore: "&#404040Random potion effects||&#404040every few jumps"
 
-    hardcore:
-      material: "skeleton_skull"
-      name: "&#00D4FF&lHardcore"
-      lore: "&#404040Lose all rewards on fall||&#404040No second chances."
-
   spectator:
     name: "&#FFFFFFSpectator"