ワードミュートで正規表現のフラグに対応

[poppingmoon]

ワードミュートの正規表現にm, i, u, sのフラグが含まれている場合にRegExpの対応するプロパティを変更するようにしました

Fix #580

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 18 lines in your changes are missing coverage. Please review.

Project coverage is 36.57%. Comparing base (017c89e) to head (1b7d2db).

Files	Patch %	Lines
lib/repository/note_repository.dart	0.00%	18 Missing :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #581 +/- ## =========================================== - Coverage 36.60% 36.57% -0.04% =========================================== Files 257 257 Lines 13587 13601 +14 =========================================== Hits 4974 4974 - Misses 8613 8627 +14 ```

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