Add prefers-dark-theme

src/main.jsx

@@ -103,11 +103,12 @@ const App = ({}) => {
         setEventi(eventi)
     }, [source])
 
-    const [theme, setTheme] = useState(localStorage.getItem("theme") ?? "light")
+    const [theme, setTheme] = useState(localStorage.getItem("theme") ?? (window.matchMedia('(prefers-color-scheme: dark)').matches ? "dark" : "light"))
 
     document.body.classList.toggle("dark-mode", theme === "dark")
     localStorage.setItem("theme", theme)
 
+
     return (
         <>
             <Toolbar