feat(web): improve slideshow quality of life (#18778)

* Add a new setting to toggle autoplay when showing the slideshow.
* Fix an issue where the slideshow would restart automatically when
navigating after it was paused.
* Add a keyboard shortcut 's' to start the slideshow from the asset
viewer.
* Add a keyboard shortcut ' ' to toggle the slideshow play/paused.
* Change the timeout for hiding the slideshow controls from 10 to 2.5
seconds.
* Add English translation for the 'autoplay_slideshow' setting.

Co-authored-by: Alex <alex.tran1502@gmail.com>

web/src/lib/components/asset-viewer/photo-viewer.svelte

@@ -113,6 +113,8 @@
     });
   };
 
+  const onPlaySlideshow = () => ($slideshowState = SlideshowState.PlaySlideshow);
+
   $effect(() => {
     if (isFaceEditMode.value && $photoZoomState.currentZoom > 1) {
       zoomToggle();
@@ -206,6 +208,8 @@
 
 <svelte:document
   use:shortcuts={[
+    { shortcut: { key: 'z' }, onShortcut: zoomToggle, preventDefault: true },
+    { shortcut: { key: 's' }, onShortcut: onPlaySlideshow, preventDefault: true },
     { shortcut: { key: 'c', ctrl: true }, onShortcut: onCopyShortcut, preventDefault: false },
     { shortcut: { key: 'c', meta: true }, onShortcut: onCopyShortcut, preventDefault: false },
     { shortcut: { key: 'z' }, onShortcut: zoomToggle, preventDefault: false },