feat(registration): support next input element with ENTER key

src/routes/registration/+page.svelte

@@ -101,6 +101,11 @@
 								<label for="firstname" class="block text-lg font-bold mb-2 sr-only">Vorname</label>
 								<div class="relative">
 									<input
+										on:keydown={(e) => {
+											if (e.keyCode === 13) {
+												document.getElementById('lastname')?.focus();
+											}
+										}}
 										type="text"
 										id="firstname"
 										name="firstname"