message: Finalize changelog for v1.38.4
diff: # Change Log
  -## [1.38.4] - Development
  +## [1.38.4] - 2022-04-06
  ### Added
  - Added [JavaScript bindings](https://github.com/AcademySoftwareFoundation/MaterialX/tree/main/javascript) for MaterialXCore, MaterialXFormat, and MaterialXGenGlsl.
  - Added a sample [Web Viewer](https://academysoftwarefoundation.github.io/MaterialX/), built and deployed through GitHub Actions.
  - Added a MaterialX graph for the [glTF PBR](libraries/bxdf/gltf_pbr.mtlx) shading model.
  - Added new 'worleynoise2d' and 'worleynoise3d' nodes, with implementations in GLSL, OSL, and MDL.
  +- Added new 'surface_unlit' node, with implementations in GLSL, OSL, and MDL.
  - Added support for the glTF geometry format in MaterialXRender and MaterialXView.
  ### Changed
  - Moved the MaterialX project to the [Academy Software Foundation GitHub](https://github.com/AcademySoftwareFoundation/MaterialX).
  - Removed hardcoded references to "libraries" in calls to GenContext::registerSourceCodeSearchPath. (See Developer Notes below for additional details.)
  - Improved the accuracy of mx_ggx_dir_albedo_analytic and mx_fresnel_conductor in GLSL.
  +- Updated the PyBind11 library to version 2.9.0.
  ### Fixed
  - Aligned GLSL and MDL implementations of 'fractal3d' with OSL.
  