LibGfx+LibWeb: Move "transparent" keyword into Color::from_string()

It seemed odd to have this one color handled separately, when
`Color::from_string()` implements all other CSS colors.

Userland/Libraries/LibGfx/Color.cpp

@@ -245,6 +245,9 @@ Optional<Color> Color::from_string(const StringView& string)
         { 0x000000, nullptr }
     };
 
+    if (string == "transparent")
+        return Color::from_rgba(0x00000000);
+
     for (size_t i = 0; !web_colors[i].name.is_null(); ++i) {
         if (string == web_colors[i].name)
             return Color::from_rgb(web_colors[i].color);

Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp

@@ -2087,8 +2087,6 @@ Optional<Color> Parser::parse_color(ParsingContext const&, StyleComponentValueRu
     // https://www.w3.org/TR/css-color-3/
     if (component_value.is(Token::Type::Ident)) {
         auto ident = component_value.token().ident();
-        if (ident.equals_ignoring_case("transparent"))
-            return Color::from_rgba(0x00000000);
 
         auto color = Color::from_string(ident.to_string().to_lowercase());
         if (color.has_value())