Expose 'aliased_html' in doc JSON (#10117)

This can be useful for external doc generators, to detect where Crystal decides to linkify types and such.

src/compiler/crystal/tools/doc/type.cr

@@ -771,7 +771,8 @@ class Crystal::Doc::Type
       builder.field "program", program?
       builder.field "enum", enum?
       builder.field "alias", alias?
-      builder.field "aliased", alias_definition.to_s
+      builder.field "aliased", alias? ? alias_definition.to_s : nil
+      builder.field "aliased_html", alias? ? formatted_alias_definition : nil
       builder.field "const", const?
       builder.field "constants", constants
       builder.field "included_modules" do