Short title (summary): Fix typos

Description
Found via codespell -S ./build,./benchmarks/competition -L vie,persan,fo,ans,larg,indx,shft,carryin and typos --hidden --format brief

Type of change

• Bug fix
• Optimization
• New feature
• Refactor / cleanup
• Documentation / tests
• Other (please describe):

How to verify / test

• Add additional tests to verify bugs or new features.
• If you claim performance gains, you should provide benchmark numbers using high quality benchmarking code.

Please read before contributing:

• CONTRIBUTING: https://github.com/simdutf/simdutf/blob/master/CONTRIBUTING.md

If you can, we recommend running our tests with the sanitizers turned on.
For non-Visual Studio users, it is as easy as doing:

cmake -B build -D SIMDUTF_SANITIZE=ON
cmake --build build
ctest --test-dir build

Our CI checks, among other things, for trailing whitespace.

Checklist before submitting

• I added/updated tests covering my change (if applicable)
• Code builds locally and passes my check
• Documentation / README updated if needed
• Commits are atomic and messages are clear
• I linked the related issue (if applicable)

Final notes

• For large PRs, prefer smaller incremental PRs or request staged review.

Thanks for the contribution!