Fix: Feed-Thumbnails are broken

_posts/2012-07-04-first-final-release.md

@@ -4,7 +4,7 @@ section-type: post
 title: First final release!
 tags: [ 'release', '0.1' ]
 author: "flokuep"
-image: "release-01.png"
+image: "/img/posts/release-01.png"
 ---
 ![Release 1]({{site.baseurl}}/img/posts/release-01.png){:.post-banner}
 

_posts/2012-12-21-second-release.md

@@ -4,7 +4,7 @@ section-type: post
 title: Second version released!
 tags: [ 'release', '0.2' ]
 author: "flokuep"
-image: "release-02.png"
+image: "/img/posts/release-02.png"
 ---
 ![Release 2]({{site.baseurl}}/img/posts/release-02.png){:.post-banner}
 

_posts/2017-09-28-blue-sunrise-is-released.md

@@ -4,7 +4,7 @@ section-type: post
 title: Blue Sunrise is released!
 tags: [ 'release', '0.4' ]
 author: "flokuep"
-image: "release-0.4.png"
+image: "/img/posts/release-0.4.png"
 ---
 ![Release of Vocaluxe (Blue Sunrise)]({{site.baseurl}}/img/posts/release-0.4.png){:.post-banner}