docs: update doc

README.md

@@ -6,7 +6,7 @@
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-kuroshiro is a Japanese language utility mainly for converting Japanese sentence to Hiragana, Katakana or Romaji with furigana and okurigana modes supported.
+kuroshiro is a Japanese language library for converting Japanese sentence to Hiragana, Katakana or Romaji with furigana and okurigana modes supported.
 
 *Read this in other languages: [English](README.md), [日本語](README.jp.md), [简体中文](README.zh-cn.md), [繁體中文](README.zh-tw.md).*