[rlgl][rmodels] Add instranceTransform shader location index #4538 (#4579)

examples/shaders/resources/shaders/glsl330/lighting_instancing.vs

@@ -25,7 +25,7 @@ void main()
     // Send vertex attributes to fragment shader
     fragPosition = vec3(instanceTransform*vec4(vertexPosition, 1.0));
     fragTexCoord = vertexTexCoord;
-    //fragColor = vertexColor;
+    fragColor = vec4(1.0);
     fragNormal = normalize(vec3(matNormal*vec4(vertexNormal, 1.0)));
 
     // Calculate final vertex position, note that we multiply mvp by instanceTransform