🥅 Added info why quiz can't get imported

frontend/src/routes/docs/develop.svelte

@@ -25,7 +25,7 @@
 
 	<h4>Frontend</h4>
 	<ul>
-		<li><a href="https://pnpm.io/">pNpM</a></li>
+		<li><a href="https://pnpm.io/">pnpm</a></li>
 	</ul>
 
 	<h2>Setup</h2>

frontend/src/routes/import.svelte

@@ -43,6 +43,8 @@
 
 		if (res.status === 200) {
 			window.location.href = '/overview';
+		} else if (res.status === 400) {
+			alert("This quiz isn't (yet) supported!");
 		} else {
 			alert('Error importing quiz');
 		}