LibWeb: Add an initial implementation of SVG text-anchor

This only handles very simple <text> elements, but this is enough (with
the font-size changes) to improve the badges on the GitHub README a fair
bit.

Userland/Libraries/LibWeb/SVG/AttributeParser.h

@@ -125,6 +125,12 @@ enum class FillRule {
     Evenodd
 };
 
+enum class TextAnchor {
+    Start,
+    Middle,
+    End
+};
+
 class AttributeParser final {
 public:
     ~AttributeParser() = default;