url(foo.png)
url(close\)parens)
url('foo.png')
url("foo.png")
url('foo\
bar.png')
url("foo\
bar.png")

@import url("https://cdn.jsdelivr.net/npm/prismj1.19.0/themes/prism-dark.css");
@import url("https://cdn.jsdelivr.net/npm/prismjs/themes/prism-dark.css");

----------------------------------------------------

[
	["url", [
		["function", "url"],
		["punctuation", "("],
		"foo.png",
		["punctuation", ")"]
	]],
	["url", [
		["function", "url"],
		["punctuation", "("],
		"close\\)parens",
		["punctuation", ")"]
	]],
	["url", [
		["function", "url"],
		["punctuation", "("],
		["string", "'foo.png'"],
		["punctuation", ")"]
	]],
	["url", [
		["function", "url"],
		["punctuation", "("],
		["string", "\"foo.png\""],
		["punctuation", ")"]
	]],
	["url", [
		["function", "url"],
		["punctuation", "("],
		["string", "'foo\\\r\nbar.png'"],
		["punctuation", ")"]
	]],
	["url", [
		["function", "url"],
		["punctuation", "("],
		["string", "\"foo\\\r\nbar.png\""],
		["punctuation", ")"]
	]],
	["atrule", [
		["rule", "@import"],
		["url", [
			["function", "url"],
			["punctuation", "("],
			["string", "\"https://cdn.jsdelivr.net/npm/prismj1.19.0/themes/prism-dark.css\""],
			["punctuation", ")"]
		]],
		["punctuation", ";"]
	]],
	["atrule", [
		["rule", "@import"],
		["url", [
			["function", "url"],
			["punctuation", "("],
			["string", "\"https://cdn.jsdelivr.net/npm/prismjs/themes/prism-dark.css\""],
			["punctuation", ")"]
		]],
		["punctuation", ";"]
	]]
]

----------------------------------------------------

Checks for url(), unquoted, single-quoted and double-quoted.
