
So I ended up making my own, and I wanted to share it here for anyone that might find it useful.
Link: https://github.com/tragicmuffin/6502-npp-syntax
I used NESASM3 to make my game, so I have a file that highlights directives and things for that, but I also included a general file that just highlights 6502 syntax.
If anyone would like highlighting for directives of a different assembler, send me a link to the assembler's commands and I'll make a separate file for it.
Enjoy!