add materials and lights placeholder

threejs/lessons/threejs-materials-and-lights.md

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+Title: Three.js Materials and Lights
+Description: Materials and Lights
+
+This article is part of a series of articles about three.js. The
+first article is [three.js fundamentals](three-fundamentals.html). If
+you haven't read yet you might want to consider starting there.
+
+TBD