Support ID selectors inside :has()

[yetval]

parse_relative_selector() only accepts IDENT, ., and * tokens in a :has() argument, so any ID selector raises:

>>> parse("div:has(> #foo)")
SelectorSyntaxError: Expected an argument, got <HASH 'foo' at 10>

This works in browsers, which implement the full relative-selector grammar.

This PR adds HASH to the accepted token types in the argument loop. No changes are needed in the translation layer—the token reparse and XPath translation already handle Hash nodes, escaped identifiers included:

>>> HTMLTranslator().css_to_xpath(r"div:has(> #foo\.bar)")
"descendant-or-self::div[./*[@id = 'foo.bar']]"

Tests added for parsing, specificity, repr round-trip, XPath translation, and the error case (:has(a #b) still rejects the descendant combinator).

Downstream report: D4Vinci/Scrapling#433

[wRAR]

This should be fixed by #179.

[yetval]

This should be fixed by #179.

Seems like I missed that I will close this pr in favor of it.