add table missing attribute list

docs/modules/contributions/pages/contributions.adoc

@@ -293,6 +293,7 @@ a| Abandoned but ther is a fork of the project that has been updated and can be
 
 IGUI is a minimalistic immediate gui for jMonkeyEngine. It is built around Picture and BitmapText classes.
 
+[cols="2", options="header"]
 |===
 
 a| *Contact person*