Scrolling of graphical landing pages broken in Restricted mode

[Jaifroid]

First reported downstream in https://github.com/kiwix/kiwix-js-windows/issues/475, the graphical landing page of recent ZIMs does not scroll when loaded with jQuery mode. This issue is serious because it also affects the libzim branch of this Repo in ServiceWorker mode, suggesting that it's a wider issue than just the lack of JS support in jQuery mode.

These graphical landing pages are very troublesome. They render extremely poorly on Android (extremely slow outside of the OPFS implementation), and also break the WebP polyfill due to overloading the Emscripten engine and filling up the memory.