Add in-game field manual on the pause screen

A [?] HELP button (or H key) on the pause screen opens a seven-page
technical manual: controls, run loop, arsenal, mutations, implants,
bestiary and pressure/defense math. List pages render live from the
WEAPONS/ITEMS/PERKS/ENEMY_TYPES/BOSS_DEFS tables so values never drift.
Also unifies the sfxbank fetch cache-buster with the v36 bump.

js/sprites.js

@@ -73,7 +73,7 @@ const Sprites = {
       const img = new Image();
       img.onload = () => { this.imgs[name] = img; if (--pending === 0) G.imagesLoaded = true; };
       img.onerror = () => { if (--pending === 0) G.imagesLoaded = true; };
-      img.src = 'assets/' + name + '.png?v=35';
+      img.src = 'assets/' + name + '.png?v=36';
     }
   },