Add better warning borders

[codecov[bot]]

Codecov Report

Base: 69.62% // Head: 71.08% // Increases project coverage by +1.45% :tada:

Coverage data is based on head (741f6b3) compared to base (d592498). Patch coverage: 96.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #13 +/- ## ========================================== + Coverage 69.62% 71.08% +1.45% ========================================== Files 8 8 Lines 270 287 +17 ========================================== + Hits 188 204 +16 - Misses 82 83 +1 ``` | [Impacted Files](https://codecov.io/gh/rebelappstudio/accessibility_tools/pull/13?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=rebelappstudio) | Coverage Δ | | |---|---|---| | [lib/src/accessibility\_tools.dart](https://codecov.io/gh/rebelappstudio/accessibility_tools/pull/13/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=rebelappstudio#diff-bGliL3NyYy9hY2Nlc3NpYmlsaXR5X3Rvb2xzLmRhcnQ=) | `90.74% <96.00%> (+0.63%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=rebelappstudio). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=rebelappstudio)

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