LibUnicode: Parse UCD Scripts.txt and generate as a Unicode property

There are a couple of minor nuances with parsing script values, compared
to other properties. In Scripts.txt, the UCD file lists the full name of
each script; other properties, like General Category, list the shorter
name in their primary files. This means that the aliases listed in
PropertyValueAliases.txt are reversed for script values.

Userland/Libraries/LibUnicode/Forward.h

@@ -14,6 +14,7 @@ enum class Condition;
 enum class GeneralCategory : u64;
 enum class Locale;
 enum class Property : u64;
+enum class Script;
 enum class WordBreakProperty;
 
 struct SpecialCasing;