Add KHR_meshopt_compression and EXT_meshopt_compression

Author: UX3D-haertl

README.md

@@ -33,11 +33,13 @@ Link to the live [glTF 2.0 Sample Viewer](https://github.khronos.org/glTF-Sample
 - [KHR_materials_volume_scatter](https://github.com/KhronosGroup/glTF/blob/e17468db6fd9ae3ce73504a9f317bd853af01a30/extensions/2.0/Khronos/KHR_materials_volume_scatter/README.md)
     - [x] For dense volumes using KHR_materials_diffuse_transmission
     - [ ] For sparse volumes using KHR_materials_transmission
+- [x] [KHR_meshopt_compression](https://github.com/KhronosGroup/glTF/pull/2517)
 - [x] [KHR_mesh_quantization](https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Khronos/KHR_mesh_quantization)
 - [x] [KHR_texture_basisu](https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Khronos/KHR_texture_basisu)
 - [x] [KHR_texture_transform](https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Khronos/KHR_texture_transform)
 - [x] [KHR_xmp_json_ld](https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Khronos/KHR_xmp_json_ld)
 - [x] [EXT_mesh_gpu_instancing](https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Vendor/EXT_mesh_gpu_instancing)
+- [x] [EXT_meshopt_compression](https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Vendor/EXT_meshopt_compression)
 - [x] [EXT_texture_webp](https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Vendor/EXT_texture_webp)
 
 ### UI