Added [models] example - skybox loading and drawing

examples/models/skybox/skybox.fs

@@ -0,0 +1,19 @@
+#version 330
+
+// input vertex attributes (from vertex shader)
+in vec3 fragPosition;
+
+// input uniform values
+uniform samplerCube environmentMap;
+
+// output fragment color
+out vec4 finalColor;
+
+void main()
+{
+    // fetch color from texture map
+    vec3 color = texture(environmentMap, fragPosition).rgb;
+
+    // calculate final fragment color
+    finalColor = vec4(color, 1.0);
+}