fix: load images (#174)

from https://via.placeholder.com using crossorigin="anonymous" attribute

Author: ivanbtrujillo

content/tutorial/01-svelte/07-lifecycle/01-onmount/README.md

@@ -2,8 +2,6 @@
 title: onMount
 ---
 
-> The images in this exercise don't currently work. You can switch to the old tutorial instead: https://svelte.dev/tutorial/onmount
-
 Every component has a _lifecycle_ that starts when it is created, and ends when it is destroyed. There are a handful of functions that allow you to run code at key moments during that lifecycle.
 
 The one you'll use most frequently is `onMount`, which runs after the component is first rendered to the DOM.

content/tutorial/01-svelte/07-lifecycle/01-onmount/app-a/src/lib/App.svelte

@@ -8,6 +8,7 @@
 	{#each photos as photo}
 		<figure>
 			<img
+				crossorigin="anonymous"
 				src={photo.thumbnailUrl}
 				alt={photo.title}
 			/>

content/tutorial/01-svelte/07-lifecycle/01-onmount/app-b/src/lib/App.svelte

@@ -17,6 +17,7 @@
 	{#each photos as photo}
 		<figure>
 			<img
+				crossorigin="anonymous"
 				src={photo.thumbnailUrl}
 				alt={photo.title}
 			/>