Improve the pack handling experience somewhat

- Include links for the stock packs

- Show completion amount and total time for played packs

- Expose a list of all other packs the player has played

- Allow forgetting a pack

- Jump to the current level when reopening a pack

- Highlight the current level in the level browser, and scroll to it

index.html

@@ -85,6 +85,7 @@
         </div>
     </main>
     <script>
+        // FIXME not quite good enough; we'll get loading forever if there's a syntax error in the js
         document.querySelector('#failed').setAttribute('hidden', '');
         document.querySelector('#loading').removeAttribute('hidden');
     </script>