LibWeb: Add list-style-type: lower-alpha and lower-latin support

They achieve the same, a list which markers are lowercase (latin)
characters.

Userland/Libraries/LibWeb/CSS/Identifiers.json

@@ -104,6 +104,8 @@
   "line-through",
   "list-item",
   "lowercase",
+  "lower-alpha",
+  "lower-latin",
   "medium",
   "move",
   "ne-resize",

Userland/Libraries/LibWeb/CSS/StyleProperties.cpp

@@ -578,6 +578,10 @@ Optional<CSS::ListStyleType> StyleProperties::list_style_type() const
         return CSS::ListStyleType::Decimal;
     case CSS::ValueID::DecimalLeadingZero:
         return CSS::ListStyleType::DecimalLeadingZero;
+    case CSS::ValueID::LowerAlpha:
+        return CSS::ListStyleType::LowerAlpha;
+    case CSS::ValueID::LowerLatin:
+        return CSS::ListStyleType::LowerLatin;
     default:
         return {};
     }

Userland/Libraries/LibWeb/CSS/StyleValue.h

@@ -160,6 +160,8 @@ enum class ListStyleType {
     Square,
     Decimal,
     DecimalLeadingZero,
+    LowerAlpha,
+    LowerLatin,
 };
 
 enum class Overflow : u8 {

Userland/Libraries/LibWeb/Layout/ListItemMarkerBox.cpp

@@ -5,11 +5,14 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/StringBuilder.h>
 #include <LibGfx/Painter.h>
 #include <LibWeb/Layout/ListItemMarkerBox.h>
 
 namespace Web::Layout {
 
+constexpr auto lower_alpha = "abcdefghijklmnopqrstuvwxyz";
+
 ListItemMarkerBox::ListItemMarkerBox(DOM::Document& document, CSS::ListStyleType style_type, size_t index)
     : Box(document, nullptr, CSS::StyleProperties::create())
     , m_list_style_type(style_type)
@@ -74,6 +77,10 @@ void ListItemMarkerBox::paint(PaintContext& context, PaintPhase phase)
             m_index < 10 ? String::formatted("0{}.", m_index) : String::formatted("{}.", m_index),
             Gfx::TextAlignment::Center);
         break;
+    case CSS::ListStyleType::LowerAlpha:
+    case CSS::ListStyleType::LowerLatin:
+        context.painter().draw_text(enclosing, number_to_alphabet(m_index, lower_alpha), Gfx::TextAlignment::Center);
+        break;
     case CSS::ListStyleType::None:
         return;