Add support for games that use DDS textures

[luizzeroxis]

Description

Fix #1907

Some games use the official GM-GPUTextureCompression extension to use GPU compressed textures. One of the formats supported is BCN compression, which uses the DDS format, at least on Windows. This PR aims to allow games using that to be modded.

Caveats

Although you can load it, there's no support for saving these textures in their original format, so it just saves in PNG format and gives a warning to the user. This works, but obviously will have a performance impact. This compression format is lossy anyway.

Notes

There's other formats supported by this extension, and in other operating systems, hopefully this can be addressed in future PRs.