feat: add segment api

[zh-lx]

增加 segment 分词 api。

close #259

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Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 100.00%. Comparing base (0a1adcf) to head (2fdbd9a). Report is 18 commits behind head on main.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #265 +/- ## ========================================== Coverage 100.00% 100.00% ========================================== Files 23 25 +2 Lines 25861 26142 +281 Branches 458 494 +36 ========================================== + Hits 25861 26142 +281 ```

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