add comment for isAvaliable method

source/RobotAPI/libraries/skills/provider/SpecializedSkill.h

@@ -76,6 +76,7 @@ namespace armarx
             }
 
         private:
+            /// Override this method if you want to disable a skill based on certain conditions
             virtual bool isAvailable(const SpecializedInitInput&) const
             {
                 return true;