Han unification regex is incorrect

[KarolS]

The regex tries to use 5-digit Unicode escapes, but Unicode escapes are only 4-digit, which makes it not work.

For example this fragment: \u20000-\u2A6DF is interpreted as 3 Unicode ranges:

• U+2000 (which is not a Han character)

• from 0 (U+0030) to U-2A6D (which encompasses tons of various characters, including the entire Latin alphabet, but no Han characters)

• F (U+0045)

I guess the regex should be rewritten using surrogates, like the emoji one.