Add highlighting for Zig object notation files + other fixes

[aidenfoxivey]

Hi there! First time contributor to this repo so I'm unsure whether my formatting is appropriate.

I just added the inf and nan fields that I read were required in https://github.com/ziglang/zig/pull/20271. I've also removed highlighting for &, seeing as though ampersands aren't permitted in Zig. (to the beset of my knowledge)

Hoping to help close #71. Criticisms would be greatly appreciated. :)

Cheers!

• Aiden