missing include

Former-commit-id: 3304471f4e83fb44b45a2b5cda65bd34029beed4

include/igl/viewer/ViewerCore.h

@@ -15,6 +15,8 @@
 #include <igl/viewer/OpenGL_state.h>
 
 #include <igl/igl_inline.h>
+#include <Eigen/Geometry>
+#include <Eigen/Core>
 
 namespace igl
 {