Update tutorial.md (#8531)

* Update tutorial.md

referencing `main.jsx` or `index.js` depending on the bundler used.

* Update contributors.yml

Adding underager to contributors.yml

contributors.yml

@@ -22,3 +22,4 @@
 - timdorr
 - turansky
 - vijaypushkin
+- underager

docs/getting-started/tutorial.md

@@ -170,7 +170,7 @@ export default function Invoices() {
 }
 ```
 
-Finally, let's teach React Router how to render our app at different URLs by creating our first "Route Config" inside of `main.jsx`.
+Finally, let's teach React Router how to render our app at different URLs by creating our first "Route Config" inside of `main.jsx` or `index.js`.
 
 ```tsx lines=[2,4-5,13-19] filename=src/main.jsx
 import { render } from "react-dom";