fix: t6 modman textures (#849)

* feat: dynamically decompress bc5 textures for modman

* chore: restructure image format class

* chore: keep dds file conversions

* chore: convert all kinds of webgl unsupported formats

* chore: add decompressors for remaining formats

* chore: always set full alpha if available on bc4 and bc5 decompression

src/ObjImage/Image/TextureConverter.h

@@ -15,7 +15,6 @@ namespace image
         std::unique_ptr<Texture> Convert();
 
     private:
-        static constexpr uint64_t Mask1(unsigned length);
         void SetPixelFunctions(unsigned inBitCount, unsigned outBitCount);
 
         void CreateOutputTexture();