feat: add nasm language

[mtoohey31]

This pull request adds nasm assembly as a language.

Closes #3329.

Under the issue mentioned above, there is a discussion about how to support various assembly flavours. I think the best approach is to add flavour-specific language definitions with the appropriate grammars, then users can override the file-types values as desired in their local languages.toml files so that the .asm extension (or whichever extension they're using) is recognized as the flavour that they're working with. Since nasm will be the only flavour supported so far after the changes in this merge request, I've included the .asm extension under nasm's file-types so that there is at least some syntax highlighting out of the box, even though it might not be for the right flavour. If there's a different approach that might work better though, just let me know and I can rework things.

Also, CC @naclsn (the original author of the grammar and queries). I hope you don't mind me including your work here; I've copied the queries pretty much verbatim, only I've removed some todo-related comments that probably don't belong in the version inside this repository, and I've uncommented the (ERROR) @error highlight.

Edit: oh, and here's a screenshot:

[naclsn]

Neat, thanks for using my work!

Like most language with (C-like) preprocessor, the written code can be syntactically invalid despite being correct. This is why I had the same approach as the C highlight queries to not have @error at all.

[mtoohey31]

Neat, thanks for using my work!

Like most language with (C-like) preprocessor, the written code can be syntactically invalid despite being correct. This is why I had the same approach as the C highlight queries to not have @error at all.

Ah, that makes sense, thanks for taking a look at the changes! I've removed that query in eda2cc6.

[the-mikedavis]

If the preprocessor stuff is like the C preprocessor, these might fall under @keyword.directive https://docs.helix-editor.com/master/themes.html#syntax-highlighting

[mtoohey31]

I think you're right that @keyword.directive makes more sense. I've switched it to that in df21375 along with a few other improvements.