LibUnicode: Add decomposition mappings and Unicode normalization

The mappings are exposed via `Unicode::code_point_decomposition(u32)`
and `Unicode::code_point_decompositions()`, the latter being useful for
reverse searching a code point from its decomposition.

The normalization code does not make use of `Quick_Check` props (https://www.unicode.org/reports/tr44/#Decompositions_and_Normalization),
meaning no quick check optimizations.

Userland/Libraries/LibUnicode/CMakeLists.txt

@@ -4,6 +4,7 @@ set(SOURCES
     CharacterTypes.cpp
     CurrencyCode.cpp
     Emoji.cpp
+    Normalize.cpp
     ${UNICODE_DATA_SOURCES}
 )