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/molecules/PaginationDots.svelte

@@ -14,7 +14,7 @@
         class:active={index === currentIndex}
         class:small={index < currentIndex - 2 || index > currentIndex + 2}
         class:hidden={index < currentIndex - 3 || index > currentIndex + 3}
-        on:click={() => dispatch('goToIndex', { index })}
+        on:click={() => dispatch('goToIndex', index)}
     >
         <button aria-label="Go to photo #{index + 1}"></button>
     </li>