LibWeb: Resolve CSS text-decoration from value list

This detects and resolves these in the text-decoration property, in any
order:

- text-decoration-color
- text-decoration-line
- text-decoration-style

Only the solid underline renders, but all three sub-properties are
assigned correctly.

Userland/Libraries/LibWeb/CSS/Identifiers.json

@@ -185,6 +185,7 @@
   "visible",
   "vertical-text",
   "wait",
+  "wavy",
   "wrap",
   "wrap-reverse",
   "w-resize",