added link to german translation

README.md

@@ -96,6 +96,8 @@ Thanks [Nicolas Barradeau](https://twitter.com/nicoptere) and [Karim Naaji](http
 
 Thanks [Andrea Rovescalli](https://www.earove.info) for the Italian [translation (italiano)](?lan=it)
 
+Thanks [Michael Tischer](http://www.mitinet.de) for the German [translation (deutsch)](?lan=de)
+
 Thanks to everyone who has believed in this project and [contributed with fixes](https://github.com/patriciogonzalezvivo/thebookofshaders/graphs/contributors) or donations.
 
 ## Get new chapters
@@ -103,3 +105,4 @@ Thanks to everyone who has believed in this project and [contributed with fixes]
 Sign up for the news letter or [follow it on Twitter](https://twitter.com/bookofshaders)
 
  <form style="border:1px solid #ccc;padding:3px;text-align:center;" action="https://tinyletter.com/thebookofshaders" method="post" target="popupwindow" onsubmit="window.open('https://tinyletter.com/thebookofshaders', 'popupwindow', 'scrollbars=yes,width=800,height=600');return true"><a href="https://tinyletter.com/thebookofshaders"><p><label for="tlemail">Enter your email address</label></p></a><p><input type="text" style="width:140px" name="email" id="tlemail" /></p><input type="hidden" value="1" name="embed"/><input type="submit" value="Subscribe" /><p><a href="https://tinyletter.com" target="_blank"></a></p></form>
+