Approve Shu infantry handpainted sprite v8

src/game/data/unitAssets.ts

@@ -58,6 +58,10 @@ export function unitTextureVariantKeys(baseKey: string) {
   return keys.length > 0 ? keys : [baseKey];
 }
 
+export function hasUnitSheetAsset(key: string) {
+  return unitSheetAssetsByKey.has(key);
+}
+
 export function loadUnitSheets(scene: Phaser.Scene, keys: Iterable<string>, onReady: () => void) {
   const uniqueKeys = Array.from(new Set(keys));
   const missingSheets = uniqueKeys