Add test gltf avatar and update ground/sky to match a bit

...ssets/avatars/dodec/AvatarHand_L/AvatarDodeca_Texture.png

public/assets/avatars/dodec/AvatarHand_L/Avatar_HandL.bin

public/assets/avatars/dodec/AvatarHand_L/Avatar_HandL.gltf

...ssets/avatars/dodec/AvatarHand_R/AvatarDodeca_Texture.png

public/assets/avatars/dodec/AvatarHand_R/Avatar_HandR.bin

public/assets/avatars/dodec/AvatarHand_R/Avatar_HandR.gltf

...ts/avatars/dodec/DodecAvatarGLTF/AvatarDodeca_Texture.png

...assets/avatars/dodec/DodecAvatarGLTF/DodecAvatar_Head.bin

...ssets/avatars/dodec/DodecAvatarGLTF/DodecAvatar_Head.gltf

public/assets/grid.png

public/index.html