fix form validation

src/ui/pages/batch-save-urls.html

@@ -14,7 +14,7 @@
 	<header>
 		<div class="header-buttons">
 			<form id="addUrlForm">
-				<input id="addUrlInput" type="text">
+				<input id="addUrlInput" type="url" required>
 				<button id="addUrlButton"></button>
 			</form>
 			<div class="header-buttons-group">