Add controls for rearranging, duplicating, and deleting levels

index.html

@@ -5,6 +5,8 @@
     <title>Lexy's Labyrinth</title>
     <link rel="stylesheet" type="text/css" href="style.css">
     <link rel="shortcut icon" type="image/png" href="icon.png">
+    <!-- FIXME it would be super swell if i could load this lazily -->
+    <script src="https://cdn.jsdelivr.net/npm/sortablejs@latest/Sortable.min.js"></script>
     <script type="module" src="js/main.js"></script>
     <meta name="og:type" content="website">
     <meta name="og:image" content="https://c.eev.ee/lexys-labyrinth/og-preview.png">