fix(stream)!: Prevent slicing on non-UTF8 boundaries

[epage]

Fixes #460

[codecov[bot]]

Codecov Report

Attention: 20 lines in your changes are missing coverage. Please review.

:exclamation: No coverage uploaded for pull request base (main@d049ebd). Click here to learn what that means.

Files	Patch %	Lines
src/stream/mod.rs	25.92%	20 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #471 +/- ## ======================================= Coverage ? 41.86% ======================================= Files ? 18 Lines ? 3096 Branches ? 0 ======================================= Hits ? 1296 Misses ? 1800 Partials ? 0 ```

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[coveralls]

Pull Request Test Coverage Report for Build 7877832235

Details

• -20 of 28 (28.57%) changed or added relevant lines in 2 files are covered.
• 4 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.08%) to 41.86%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/stream/mod.rs	7	27	25.93%
<!--	Total:	8	28	28.57%	-->

Files with Coverage Reduction	New Missed Lines	%
src/ascii/mod.rs	2	54.23%
src/stream/mod.rs	2	25.71%
<!--	Total:	4		-->

Totals
Change from base Build 7877523483:	0.08%
Covered Lines:	1296
Relevant Lines:	3096

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💛 - Coveralls