Fix typo: contribution in README

[syy-shark]

Summary

• Fix the typo contibution in the README subtitle.

Validation

• git diff --check upstream/main..HEAD
• rg -n "contibution" README.md returned no matches.

Closes #1

[github-actions]

Hi! This looks like your first pull request to this repo — welcome. 🎉

A maintainer will take a look soon. While you wait:

• Make sure CI is green (the markdown lint check is informational and won't block your merge).
• Feel free to update the PR with more commits if you spot something — we won't squash until merge.
• If we ask for changes, that's normal — every PR, including ones from senior engineers, gets feedback.

Thanks for contributing.