docs: Add typo PR policy to CONTRIBUTING.md

[KaustubhOG]

Summary

Closes #4035

This PR adds documentation for the typo PR policy in CONTRIBUTING.md as requested in issue #4035.

Changes

• Added a new "Typo and Small Documentation Fixes" section
• Encourages batching multiple typo fixes together
• Clarifies when issues are needed vs. direct PRs
• Provides guidance on PR titles and exceptions for critical typos

[vercel]

@KaustubhOG is attempting to deploy a commit to the Solana Foundation Team on Vercel.

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[KaustubhOG]

Hi @jacobcreech,

This PR adds a new section, “Typo and Small Documentation Fixes,” to CONTRIBUTING.md, addressing the feedback and intent from #4035.

✅ All CI checks have passed, except for the Vercel deploy, which requires organization-level authorization.
✅ The PR has no merge conflicts and is ready for integration.

Kindly review and approve when convenient. Please let me know if any additional adjustments or clarifications are required before merge.

Thank you for your time and consideration

[jamie-osec]

Closing for #4035