Add NDS screenshot tutorial link

src/data/screenshotTutorials.ts

@@ -0,0 +1,18 @@
+import type { Platform } from "./baseRoms";
+
+export type ScreenshotTutorial = {
+  url: string;
+  emulatorName: string;
+};
+
+export const screenshotTutorials: Partial<Record<Platform, ScreenshotTutorial>> = {
+  NDS: {
+    url: "https://youtu.be/3lP7Cdk7Gpo",
+    emulatorName: "DeSmuMe",
+  },
+};
+
+export function getScreenshotTutorial(platform: Platform | undefined): ScreenshotTutorial | null {
+  if (!platform) return null;
+  return screenshotTutorials[platform] || null;
+}