🚚 update StaticRouter import

background: remix-run/react-router#8353 (comment)

`.js` extension seems to be no longer needed

This also has the added benefit of
reducing the bundle size by about 1.65kB

src/App.jsx

@@ -13,7 +13,7 @@ import {
   useLocation,
   useNavigate,
 } from 'react-router-dom'
-import { StaticRouter } from 'react-router-dom/server.js'
+import { StaticRouter } from 'react-router-dom/server'
 import {
   getGradientClassName,
   getThemeClassName,