idz: Hoist userdb code

src/idz/userdb/encoder/loadStocker.ts

@@ -0,0 +1,12 @@
+import { encodeBitmap } from "./_bitmap";
+import { LoadStockerResponse } from "../response/loadStocker";
+
+export function loadStocker(res: LoadStockerResponse) {
+  const buf = Buffer.alloc(0x00a0);
+
+  buf.writeInt16LE(0x00a8, 0x0000);
+  buf.writeUInt8(res.status, 0x0002);
+  encodeBitmap(res.backgrounds, 0x24).copy(buf, 0x0003);
+
+  return buf;
+}