Whitelist KTX for Sanity Bot

In Qt Quick 3D it is quite common to use the KTX format (.ktx) to store compressed image data.  These images files can be quite large because we need to use >2K textures to get the correct texel density, and in other cases data is composed multiple images (cubemaps, texture arrays, 3D textures) which can get quite large.  These images are generally compressed and stored into the KTX container file, and they are quite commonly greater than the 2MB Huge file limit. Discretion should still be used before accepting large KTX files, but it shouldn't be an automatic -2 from the sanity bot.