Fix typo: contribution in README

[Eatingpigx]

What does this PR do?

Fixes the typo "contibution" → "contribution" in the subtitle blockquote at the top of README.md.

Is this your first open source contribution?

• Yes — welcome! We're glad you're here. 🎉
• No

Did you follow CONTRIBUTING.md?

• I claimed the issue in a comment before starting
• My branch follows the naming convention (add-resource/..., fix-typo/..., etc.)
• My commit messages are clear and use the imperative form
• My change does only what the issue asked for — no unrelated edits

Linked issue

Closes #1

Cohort reference (optional)

[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.

[Eatingpigx]

@claude