fix: stop single-line string rules at line ends

[danielroe]

What does this change?

I split this out from #18 for ease of reviewing

the context is something like some.css (which I was trying to highlight).

a single stray apostrophe highlights the rest of the file as a string. for example, in:

a { font-family: Don't; }
b { content: "kept"; }
c { font-family: Won't; }

everything from the ' in Don't to the one in Won't comes out as string, and similarly in yaml.

the issue was that single-line string rules didn't exclude line breaks. elsewhere, javascript.js and python.js already use [^"\\\r\n], and toml's single-quoted rule does too, so this adds the same behaviour to grammars that were missing it

(I've left alone the languages where a raw newline inside a quoted string is legal, assuming it was deliberate)

yaml does allow quoted scalars to fold over lines (I learned), but only onto more-indented ones, so I handle that case as well ...

and one more (unrelated) issue, which I'm happy to split out into further PR if you like: a number of block at-rules were missing and being highlighted as selectors.

happy to make any and all changes, or feel free to directly push changes 🙏

Checklist

• npm test passes locally
• The size budget still passes (note any size impact below)
• Added/updated tests or the demo (docs/index.html) if behavior changed
• For a new grammar/theme, followed the steps in CONTRIBUTING.md

Size impact

none