Add back Hangul
Add back Hangul

It was previously included in the ngram_chars, but removed from
there in 2ab803b2fc2ff5948f9457fc8a755b1b4ac593ae.

Tatoeba/tatoeba2,Tatoeba/tatoeba2,Tatoeba/tatoeba2,Tatoeba/tatoeba2,Tatoeba/tatoeba2