feat: Add post thumbnail to show page

This commit adds a post thumbnail to the show page of a post. The thumbnail is displayed below the date and above the post title. It is an image with the source set to the URL of the post's thumbnail and alt text set to the post's title. The image has a fixed height, rounded corners, and a semi-transparent border.

resources/views/posts/show.blade.php

@@ -24,6 +24,8 @@
         <h3 class="not-prose text-sm text-center text-orange-100 font-semibold" itemprop="datePublished">
             {{ Carbon::parse($post->date)->format('F d, Y') }}
         </h3>
+        <img src="{{$post->thumbnail}}" alt="{{$post->title}} Thumbnail"
+             class="not-prose aspect-video h-80 mt-2 mb-2 mx-auto rounded-3xl border-orange-500/40 border-2"/>
         <div>
             <h1
                 class="not-prose text-3xl font-bold text-center text-transparent uppercase sm:text-4xl