Clarify unsafe intentions

[codecov[bot]]

Codecov Report

Patch and project coverage have no change.

Comparison is base (2f225a7) 68.59% compared to head (8b5684d) 68.59%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #107 +/- ## ======================================= Coverage 68.59% 68.59% ======================================= Files 4 4 Lines 242 242 ======================================= Hits 166 166 Misses 76 76 ``` | [Impacted Files](https://app.codecov.io/gh/Nullus157/bs58-rs/pull/107?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Nullus157) | Coverage Δ | | |---|---|---| | [src/encode.rs](https://app.codecov.io/gh/Nullus157/bs58-rs/pull/107?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Nullus157#diff-c3JjL2VuY29kZS5ycw==) | `78.43% <ø> (ø)` | | | [src/lib.rs](https://app.codecov.io/gh/Nullus157/bs58-rs/pull/107?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Nullus157#diff-c3JjL2xpYi5ycw==) | `100.00% <ø> (ø)` | |

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.