Viewer: Finally fix Carousel navigation depending on URL

- Instead of detecting every case using popState event or whatnot, used a Sapper page stores subscribe to go to the current photo from the URL param (findIndex in photos)
- No page transition when navigating between photos in Viewer, but runs In and Out
- Also shortened dispatches to direct value over an object

src/organisms/Pagination.svelte

@@ -22,9 +22,7 @@
             photosToAppend.forEach(photo => photo.hidden = false)
 
             // Merge new photos to show to the existing ones
-            dispatch('updatePagination', {
-                paginatedPhotos: [...paginatedPhotos, ...photosToAppend]
-            })
+            dispatch('updatePagination', [...paginatedPhotos, ...photosToAppend])
 
             // Increment current index
             currentIndex = currentIndex + photosPerPage