Updates to specification README

- Add a link to the NPR Shading Nodes specification.
- Delete a line about the removal of typedef members, as these remain active in the 1.39 specification.

Author: jstone-lucasfilm

documents/Specification/README.md

@@ -8,6 +8,7 @@ The documents in this folder comprise the complete MaterialX Specification, vers
 
 * [**MaterialX Specification**](./MaterialX.Specification.md) - the main Specification, describing definitions, core functionality and the standard node library
 * [**MaterialX Physically Based Shading Nodes**](./MaterialX.PBRSpec.md) - describes BSDF and other shading function nodes useful in constructing complex layered rendering shaders using node graphs
+* [**MaterialX NPR Shading Nodes**](./MaterialX.NPRSpec.md) - specifies shading nodes that are designed for use in non-photorealistic and stylized rendering
 * [**MaterialX Geometry Extensions**](./MaterialX.GeomExts.md) - additional MaterialX elements to define geometry-related information such as collections, properties and material assignments
 * [**MaterialX Supplemental Notes**](./MaterialX.Supplement.md) - describes recommended naming and structuring conventions for libraries of custom node definitions
 
@@ -96,7 +97,6 @@ The following new standard physically based shading nodes have been added:
 
 **Other Changes**
 
-* The <member> element for <typedef>s and the "member" attribute for inputs have been removed from the Specification, as they had never been implemented and it was not clear how they could be implemented generally.
 * The "valuerange" and "valuecurve" attributes describing expressions and function curves have been removed, in favor of using the new <curveinversecubic> / <curveuniformcubic> / etc. nodes.
 * The <geomcolor>, <geompropvalue> and <geompropvalueuniform> nodes for color3/4-type values can now take a "colorspace" attribute to declare the colorspace of the property value.
 * The &lt;cellnoise2d> and &lt;cellnoise3d> nodes now support vector<em>N</em> output types in addition to float output.