docs(contributing): fix spelling in contribution guide

[Mr444-dev]

Purpose of this PR

Fix three spelling errors in the repository's contribution guide so contributor instructions are clear.

Jira ticket

Not applicable (documentation-only spelling correction).

Changelog

Not applicable; this does not change the package or its behavior.

Documentation

Corrected "guidlines" (including the section-list entry) and "submited" in CONTRIBUTING.md.

Testing & QA (How your changes can be verified during release Playtest)

Reviewed the changed lines and ran git diff --check; no whitespace errors were reported. Unity and automated tests are not applicable to this spelling-only change.

Functional Testing

• Manual testing done
• Covered by existing automated tests
• Covered by new automated tests

Up-port

Not needed; this PR targets the repository's develop-3.x.x contribution branch.

Backports

Not needed for this documentation-only spelling correction.

[u-pr]

⚠️ Some settings were ignored in '.pr_agent.toml (repository root)' repo settings

Check the configuration's TOML syntax, permitted settings, and size limit. See the error below.

---

Error message:
Ignored prohibited settings: github_app.handle_pr_actions. Permitted settings were applied.

Configuration content:

# This is the configuration for the u-pr bot
# https://github.cds.internal.unity3d.com/unity/u-pr
# For configuration of this file:
# https://developer.portal.internal.unity.com/catalog/default/component/u-pr/docs/configuration/automatic_runs/

[github_app]
handle_pr_actions = ['opened', 'ready_for_review']  # PR events that auto-run pr_commands
pr_commands       = ["/harness-review"]             # what runs on those events
reviewer_commands = ["/harness-review"]             # what runs when @u-pr is added as reviewer

[michalChrobot]

thanks for catching those!