[docs] fix path to /tutorial/image.gif

site/content/examples/00-introduction/01-dynamic-attributes/App.svelte

@@ -1,7 +1,7 @@
 <script>
-	let src = 'tutorial/image.gif';
+	let src = '/tutorial/image.gif';
 	let name = 'Rick Astley';
 </script>
 
 <!-- {src} is short for src={src} -->
-<img {src} alt="{name} dancing">
+<img {src} alt="{name} dancing">

site/content/tutorial/01-introduction/03-dynamic-attributes/app-a/App.svelte

@@ -1,5 +1,5 @@
 <script>
-	let src = 'tutorial/image.gif';
+	let src = '/tutorial/image.gif';
 </script>
 
-<img>
+<img>

site/content/tutorial/01-introduction/03-dynamic-attributes/app-b/App.svelte

@@ -1,5 +1,5 @@
 <script>
-	let src = 'tutorial/image.gif';
+	let src = '/tutorial/image.gif';
 	let name = 'Rick Astley';
 </script>