Rework the user agent style sheet

[kasperisager]

After #165, the user agent style sheet is now mostly commented out which should obviously change:

alfa/packages/alfa-cascade/src/user-agent.ts

Lines 14 to 224 in d61d5f6

	export const UserAgent = Sheet.of(owner => {
	return [
	NamespaceRule.of(Namespace.HTML, None, owner),
	/**
	* @see https://html.spec.whatwg.org/#hidden-elements
	*/
	StyleRule.of(
	"[hidden], base, basefont, datalist, head, link, meta, noembed, noframes, param, rp, script, source, style, template, track, title",
	self => [Declaration.of("display", "none", false, Option.of(self))],
	owner
	)
	// // <area> elements are a little special in that while they are not rendered,
	// // they are focusable for the purpose of users interacting with the image
	// // reference of the <area> element. To accommodate this, we assign them a
	// // default display property of inline rather than none.
	// cssRule("area", {
	// display: "inline"
	// }),
	// cssRule("embed[hidden]", {
	// display: "inline",
	// height: "0",
	// width: "0"
	// }),
	// cssRule("input[type=hidden i]", {
	// display: "none !important"
	// }),
	// /**
	// * @see https://html.spec.whatwg.org/#the-page
	// */
	// cssRule("html, body", {
	// display: "block"
	// }),
	// /**
	// * @see https://html.spec.whatwg.org/#non-replaced-elements-flow-content
	// */
	// cssRule(
	// "address, blockquote, center, div, figure, figcaption, footer, form, header, hr, legend, listing, main, p, plaintext, pre, xmp",
	// {
	// display: "block"
	// }
	// ),
	// cssRule("dialog:not([open])", {
	// display: "none"
	// }),
	// cssRule("dialog", {
	// color: "black"
	// }),
	// cssRule("slot", {
	// display: "contents"
	// }),
	// /**
	// * @see https://html.spec.whatwg.org/#non-replaced-elements-phrasing-content
	// */
	// cssRule("big", {
	// fontSize: "larger"
	// }),
	// cssRule("small", {
	// fontSize: "smaller"
	// }),
	// cssRule("ruby", {
	// display: "ruby"
	// }),
	// cssRule("rt", {
	// display: "ruby-text"
	// }),
	// cssRule(":link", {
	// color: "#0000ee"
	// }),
	// cssRule(":visited", {
	// color: "#551a8b"
	// }),
	// cssRule(":link:active, :visited:active", {
	// color: "#ff0000"
	// }),
	// cssRule("mark", {
	// color: "black"
	// }),
	// /**
	// * @see https://html.spec.whatwg.org/#sections-and-headings
	// */
	// cssRule("article, aside, h1, h2, h3, h4, h5, h6, hgroup, nav, section", {
	// display: "block"
	// }),
	// cssRule("h1", {
	// fontSize: "2.00em"
	// }),
	// cssRule("h2", {
	// fontSize: "1.50em"
	// }),
	// cssRule("h3", {
	// fontSize: "1.17em"
	// }),
	// cssRule("h4", {
	// fontSize: "1.00em"
	// }),
	// cssRule("h5", {
	// fontSize: "0.83em"
	// }),
	// cssRule("h6", {
	// fontSize: "0.67em"
	// }),
	// /**
	// * @see https://html.spec.whatwg.org/#section-lists
	// */
	// cssRule("dir, dd, dl, dt, ol, ul", {
	// display: "block"
	// }),
	// cssRule("li", {
	// display: "list-item"
	// }),
	// /**
	// * @see https://html.spec.whatwg.org/#tables
	// */
	// cssRule("table", {
	// display: "table"
	// }),
	// cssRule("caption", {
	// display: "table-caption"
	// }),
	// cssRule("colgroup, colgroup[hidden]", {
	// display: "table-column-group"
	// }),
	// cssRule("col, col[hidden]", {
	// display: "table-column"
	// }),
	// cssRule("thead, thead[hidden]", {
	// display: "table-header-group"
	// }),
	// cssRule("tbody, tbody[hidden]", {
	// display: "table-row-group"
	// }),
	// cssRule("tfoot, tfoot[hidden]", {
	// display: "table-footer-group"
	// }),
	// cssRule("tr, tr[hidden]", {
	// display: "table-row"
	// }),
	// cssRule("td, th, td[hidden], th[hidden]", {
	// display: "table-cell"
	// }),
	// cssRule(
	// "colgroup[hidden], col[hidden], thead[hidden], tbody[hidden], tfoot[hidden], tr[hidden], td[hidden], th[hidden]",
	// {
	// visibility: "collapse"
	// }
	// ),
	// cssRule(":matches(table, thead, tbody, tfoot, tr) > form", {
	// display: "none !important"
	// }),
	// /**
	// * @see https://html.spec.whatwg.org/#the-hr-element-rendering
	// */
	// cssRule("hr", {
	// color: "gray"
	// }),
	// /**
	// * @see https://html.spec.whatwg.org/#the-fieldset-and-legend-elements
	// */
	// cssRule("fieldset", {
	// display: "block"
	// })
	];
	});