ASTC textures

Support for ASTC textures for cabinets.

The ASTC file type for the cabinet’s images could improve the overall game performance.

These need to have the .astc extension and be produced with [astcencode](https://github.com/ARM-software/astc-encoder](https://github.com/ARM-software/astc-encoder) with the following settings:

astcenc-avx2.exe -cl "texture.png" "texture.astc" 6x6 -exhaustive -yflip

Then all that’s left is referencing the .astc file instead of the .png in the description.yaml manifest.

#CDL