Add endless mode

Add endless mode; prevent stat booster items from being transferred or stolen

src/system/unlockables.ts

@@ -1,9 +1,12 @@
 export enum Unlockables {
+  ENDLESS_MODE,
   MINI_BLACK_HOLE
 }
 
 export function getUnlockableName(unlockable: Unlockables) {
   switch (unlockable) {
+    case Unlockables.ENDLESS_MODE:
+      return 'Endless Mode';
     case Unlockables.MINI_BLACK_HOLE:
       return 'MINI BLACK HOLE';
   }