move graphics to concepts section

README.md

@@ -72,6 +72,10 @@ A simple showcase how the controller can be addressed after
   on them. They are currently unsupported.
 - `controller` represents the `goSDN-controller`.
 
+---
+
+## Concepts
+
 <div align="center" style="margin-bottom:3em; margin-top:4em">
   <img src="documentation/figures/overview/updated_controller_architecture_overview.drawio.png" />
     <p> Overview of the controller architecture</p>
@@ -87,10 +91,6 @@ A simple showcase how the controller can be addressed after
   <p> Detailed view of plugin mechanism</p>
 </div>
 
----
-
-## Concepts
-
 The `goSDN` controllers core - also called `nucleus` - is a lightweight library
 that manages principal network domains and provides southbound interface
 operations for managed network elements.