Update director names in the imprint

- Replace the usage of base_url with link

imprint.md

@@ -21,10 +21,10 @@ Web: [https://www.hzdr.de](http://www.hzdr.de)
 ---
 #### Board of Directors
 **Scientific Director & Spokesperson**  
-Prof. Dr. Dr. h. c.Roland Sauerbrey
+Prof. Dr. Sebastian M. Schmidt
 
 **Administrative Director**  
-Dr. Ulrich Breuer
+Dr. Heike Wolke (interim)
 
 ---
 
@@ -53,5 +53,5 @@ have found on our website via our public
 ---
 
 #### Further Information
-  * [Privacy Policy]({{ base_url }}privacy.html)
-  * [Licensing]({{ base_url }}LICENSE.html)
+  * [Privacy Policy]({% link privacy.md %})
+  * [Licensing]({% link LICENSE.md %})