한글(한자) 혼용 변환 기능 추가.

[JustKode]

• 한글(한자) 혼용 변환 기능을 추가 하였습니다.
• impl.py 내의 is_valid_mode, get_format_string의 주석 또한 수정 하였습니다.
• 이에 따른 README도 수정 하였습니다.

Example

• In

hanja.translate('大韓民國은 民主共和國이다.', 'combination-text-reversed')

• Out

대한민국(大韓民國)은 민주공화국(民主共和國)이다.

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[JustKode]

@googlebot I signed it!