Added nesasm lexer

[ShyDev]

6502 assembler geared towards NES
http://nespowerpak.com/nesasm/

Never even saw ruby code before, never done pull requests.
Hopefully I did not screw up completely

[pyrmont]

Thanks for the the PR! I've made some changes and tried to explain them here with comments. Please let me know if I've inadvertently broken anything or if anything doesn't make sense!

[ShyDev]

Thanks for your time cleaning up and improving my code. It's all working great.
Can I add 2 simple rules in this pull request or it's better to open new pull request for this?
And one more question. For builtin function and macro parameters what token should I use? Name::Builtin is ok?

[pyrmont]

@ShyDev Oh, please push them to your fork. The PR is synced with it so anything you push there will show up here. I've got commit rights to that fork so the changes I've made here have actually been to your fork; make sure you pull them down with git pull if you haven't done so already and you'll be good to go.

[pyrmont]

As for the right token, it's usually more of an art than a science. Name::Builtin sounds like a good choice to me.

[pyrmont]

@ShyDev Thanks for submitting the lexer—it all looks good to me! This will be part of v3.14.0 when it comes out on 10 December 🎉