add link to debugging document

Agenda.md

@@ -174,6 +174,7 @@ Course material repository:  https://gitlab.dkrz.de/pythoncourse/material/
       <td><b>Session 2 : </b> Variables
         <ul><li>assignment</li>
             <li>names and reserved names</li>
+            <li>Call by Value vs Call by Reference</li>
         </ul>
     </td>
     <td style="vertical-align:top">  </td>
@@ -189,6 +190,7 @@ Course material repository:  https://gitlab.dkrz.de/pythoncourse/material/
             <li>floating-point</li>
             <li>complex</li>
             <li>conversion between types</li>
+            <li>None</li>
         </ul>
     </td>
     <td style="vertical-align:top">  </td>
@@ -210,7 +212,7 @@ Course material repository:  https://gitlab.dkrz.de/pythoncourse/material/
 
   <tr>
     <td style="vertical-align:top">10:05</td>
-      <td><b>Session 5 : </b> List, tuples, sets, and slices
+      <td><b>Session 5 : </b> List, tuples, sets, and arrays, slices
     </td>
     <td style="vertical-align:top">  </td>
     <td style="vertical-align:top">0.25</td>
@@ -392,7 +394,7 @@ Course material repository:  https://gitlab.dkrz.de/pythoncourse/material/
             <li>debugger</li>
         </ul>
     </td>
-    <td style="vertical-align:top">  </td>
+    <td style="vertical-align:top">[DEBUG.md](./DEBUG.md)  </td>
     <td style="vertical-align:top">0.5</td>
     <td style="vertical-align:top">Ralf</td>
   </tr>