Sync credits additions to README.md.

README.md

@@ -168,6 +168,10 @@ Ninja model and terrain, water, smoke, flare and status bar textures from OGRE.
 BlueHighway font from Larabie Fonts.
 Anonymous Pro font by Mark Simonson.
 NinjaSnowWar sounds by Veli-Pekka Tätilä.
+PBR textures from Substance Share. (https://share.allegorithmic.com)
+IBL textures from HDRLab's sIBL Archive.
+Dieselpunk Moto model by allexandr007.
+Mutant model from Mixamo.
 
 ##Documentation
 Urho3D classes have been sparsely documented using Doxygen notation. To