LibWeb: Add a handful of missing CSS "display" value identifiers

Userland/Libraries/LibWeb/CSS/Identifiers.json

@@ -83,6 +83,7 @@
   "contain",
   "content",
   "content-box",
+  "contents",
   "context-menu",
   "copy",
   "crosshair",
@@ -104,11 +105,14 @@
   "flex",
   "flex-start",
   "flex-end",
+  "flow",
+  "flow-root",
   "from-font",
   "full-size-kana",
   "full-width",
   "grab",
   "grabbing",
+  "grid",
   "groove",
   "help",
   "hidden",
@@ -177,6 +181,12 @@
   "row-resize",
   "row-reverse",
   "rtl",
+  "ruby",
+  "ruby-base",
+  "ruby-base-container",
+  "ruby-text",
+  "ruby-text-container",
+  "run-in",
   "sans-serif",
   "scroll",
   "se-resize",