docs: image gallery viewer (#905)

* add assets, photoswipe html element to body

* add single script, gallery for multiple items

* update docs for image gallery

* fix relative links

* inject image script on mount

* replace inline script

* remove facebook, twitter, pinterest sharing

* fix hover on share

* fix start img aspect radio, reduce size

* right align json script

* right align go script

* change script background

site/src/routes/[slug].svelte

@@ -12,7 +12,13 @@
     import Docs from "../components/Docs.svelte";
     export let slug;
     export let sections;
+    import { onMount } from 'svelte';
     export let tags;
+    import { initPhotoSwipeFromDOM } from '../utils/photoswipe.js';
+
+    onMount(() => {
+        initPhotoSwipeFromDOM('.zitadel-gallery');
+    });
 </script>
 
 <svelte:head>