fix: correctly parse escaped unicode characters in css selector

[7nik]

Found in https://discord.com/channels/457912077277855764/1372972353213960232
Specs: https://www.w3.org/TR/CSS22/syndata.html#characters

The unicode sequences (\123) weren't considered that caused falsy css_unused_selector and even css_expected_identifier (#\31 23 is a valid selector of id="123").

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🦋 Changeset detected

Latest commit: 5877d1a

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[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-svelte-15976-svelte.vercel.app/

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Playground

pnpm add https://pkg.pr.new/svelte@15976

[7nik]

Outside a string, a backslash followed by a newline stands for itself (i.e., a DELIM followed by a newline).

I couldn't get this behavior triggered in vanilla HTML, so I'm puzzled where it applies.