[Feature Request] Support for add-on .gxt files

[RecklessGlue540]

What should happen

I think this would be a nice addition to FusionFix, since there are a lot of people who mod cars into the game, and having the possibility of loading extra .gxt files so they can add custom names to their cars without the use of external limit adjusters would be great.

Also, I should mention that the PS3 version does already seem to support this.
It has them in the root of the update folder, all having "2" appended to their names like below:

Checklist

• Check the latest git build in case it's already implemented.
• Search for other requests of the same feature.