So if you used the Vertex buffer for each point in the icosphere the point itself is the correct vertex for a normal.
One way (if you wanted to alter this code to add it) is to simply take the point, and normalize it a la
Vector3f myNormal = vertices.get(x).normalize();
Add that into your normal array maintaining the same position as you got it from and that should do it.
But if you’re just doing a critique of this posted library… Then yes. I agree. The normals should’ve been added as well.