Fixing glTypeSize so it's always 1, as the KTX spec requires.

encoder/basisu_gpu_texture.cpp

diff --git a/encoder/basisu_gpu_texture.cpp b/encoder/basisu_gpu_texture.cpp
index 0b40297..dec769d 100644
--- a/encoder/basisu_gpu_texture.cpp
+++ b/encoder/basisu_gpu_texture.cpp
@@ -1504,6 +1504,8 @@
 		
 		header.m_pixelWidth = width;
 		header.m_pixelHeight = height;
+				
+		header.m_glTypeSize = 1;
 		
 		header.m_glInternalFormat = internal_fmt;
 		header.m_glBaseInternalFormat = base_internal_fmt;