[css-syntax-3] Typo in 4.3.8

[alin04]

Typo in https://www.w3.org/TR/css-syntax-3/#starts-with-a-valid-escape

If the first code point is not U+005D REVERSE SOLIDUS (), return false.

should say

If the first code point is not U+005C REVERSE SOLIDUS (), return false.

Note the unicode is incorrect for reverse solidus.

[tabatkins]

That's been fixed in the Editor's Draft for a while, I just haven't republished a WD for a while either. Thanks, tho!