Add .cfg (config files) highlighting

[schembriaiden]

I would like to have highlighting for .cfg files added to this theme as currently everything is white:

Default has more highlighting:

[luxonauta]

Hey 👋🏻 I just released an update, can you check if everything is working? Also, we now have Alucard—any issues or suggestions, feel free to tag me or open a PR! 💜

[luxonauta]

Hey — I pushed some updates that might fix this. Could you try the latest version and see if the issue is gone for you? 😊