LibWeb: Implement <system-color> and <deprecated-color> keywords

The spec allows for these either to be based on the OS, or to be defined
by the browser. Looking at the other browser engines, there's a mix of
the two options. Since we've had issues with using OS colors as
defaults, let's use hard-coded colors for now. Some of these are based
on the definitions in
https://html.spec.whatwg.org/multipage/rendering.html

Userland/Libraries/LibWeb/CSS/Identifiers.json

@@ -58,7 +58,12 @@
   "-libweb-palette-window",
   "-libweb-palette-window-text",
   "absolute",
+  "accentcolor",
+  "accentcolortext",
   "active",
+  "activeborder",
+  "activecaption",
+  "activetext",
   "additive",
   "alias",
   "all",
@@ -66,8 +71,10 @@
   "alternate",
   "alternate-reverse",
   "anywhere",
+  "appworkspace",
   "auto",
   "back",
+  "background",
   "backwards",
   "baseline",
   "blink",
@@ -80,7 +87,15 @@
   "break-word",
   "browser",
   "button",
+  "buttonborder",
+  "buttonface",
+  "buttonhighlight",
+  "buttonshadow",
+  "buttontext",
+  "canvas",
+  "canvastext",
   "capitalize",
+  "captiontext",
   "cell",
   "center",
   "circle",
@@ -130,6 +145,8 @@
   "extra-expanded",
   "fantasy",
   "fast",
+  "field",
+  "fieldtext",
   "fine",
   "fill",
   "fit-content",
@@ -146,14 +163,22 @@
   "fullscreen",
   "grab",
   "grabbing",
+  "graytext",
   "grid",
   "groove",
   "help",
   "hidden",
   "high",
   "high-quality",
+  "highlight",
+  "highlighttext",
   "hover",
+  "inactiveborder",
+  "inactivecaption",
+  "inactivecaptiontext",
   "infinite",
+  "infobackground",
+  "infotext",
   "initial-only",
   "inline",
   "inline-block",
@@ -183,6 +208,7 @@
   "lighter",
   "linear",
   "line-through",
+  "linktext",
   "list-item",
   "local",
   "lower-alpha",
@@ -191,8 +217,12 @@
   "lowercase",
   "ltr",
   "listbox",
+  "mark",
+  "marktext",
   "max-content",
   "medium",
+  "menu",
+  "menutext",
   "middle",
   "min-content",
   "minimal-ui",
@@ -265,7 +295,10 @@
   "sans-serif",
   "scale-down",
   "scroll",
+  "scrollbar",
   "se-resize",
+  "selecteditem",
+  "selecteditemtext",
   "self-end",
   "self-start",
   "semi-condensed",
@@ -311,6 +344,11 @@
   "text-top",
   "thick",
   "thin",
+  "threeddarkshadow",
+  "threedface",
+  "threedhighlight",
+  "threedlightshadow",
+  "threedshadow",
   "to-zero",
   "top",
   "textarea",
@@ -330,9 +368,13 @@
   "uppercase",
   "vertical-text",
   "visible",
+  "visitedtext",
   "w-resize",
   "wait",
   "wavy",
+  "window",
+  "windowframe",
+  "windowtext",
   "wrap",
   "wrap-reverse",
   "x-large",