mail-hook: Rewrite by TypeScript

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 48.38710% with 16 lines in your changes are missing coverage. Please review.

Project coverage is 23.16%. Comparing base (5211887) to head (7f2fe2e).

Files	Patch %	Lines
mail-hook/index.ts	48.38%	15 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #871 +/- ## ======================================= Coverage 23.15% 23.16% ======================================= Files 173 173 Lines 15350 15353 +3 Branches 3513 3513 ======================================= + Hits 3555 3556 +1 - Misses 10367 10369 +2 Partials 1428 1428 ```

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[hideo54]

えらすぎ

[hideo54]

あなたはえら呼吸をしたことがあるか