Add test values

src/test/dda/masto_embed/resources/post.html

@@ -10,7 +10,7 @@
     </header>
     <section class="mastodon-post-content">
       <p class="mastodon-post-text">POST_TEXT</p>
-      <img class="mastodon-post-image" src="POST_IMG_URL"></img>
+      <img class="mastodon-post-image" src="https://cdn.masto.host/socialmeissagmbhde/media_attachments/files/112/432/505/467/393/505/original/0d01ddb07440328e.jpg"></img>
     </section>
     <a href="LINK_PREVIEW_URL" class="mastodon-post-link-preview" target="_blank">
       <img class="mastodon-post-link-image" src="LINK_PREVIEW_IMG_URL"></img>