docs: mdx, light/dark mode, ask (#400)

docs/src/components/theme-provider.tsx

@@ -0,0 +1,16 @@
+"use client";
+
+import { ThemeProvider as NextThemesProvider } from "next-themes";
+
+export function ThemeProvider({ children }: { children: React.ReactNode }) {
+  return (
+    <NextThemesProvider
+      attribute="class"
+      defaultTheme="dark"
+      enableSystem
+      disableTransitionOnChange
+    >
+      {children}
+    </NextThemesProvider>
+  );
+}