enh: Add support for 'hashicorp' titleLink logo

[EnMod]

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Description

This PR adds support for using our company logo in the <TitleLink /> component of <Subnav />. Now a consumer can pass titleLink={{ text: 'hashicorp' }} to the <Subnav /> and the HashiCorp logo will appear, much like how our other product options operate.

PR Checklist 🚀

Items in this checklist may not may not apply to your PR, but please consider each item carefully.

• Add Asana and Preview links above.
• Conduct thorough self-review.
• Add or update tests as appropriate.
• Conduct reasonable cross browser testing for both compatibility and responsive behavior (We have a Sauce Labs account for this, if you don't have access, just ask!).
• Conduct reasonable accessibility review (use the WAS as a guide or an axe browser plugin until we establish more formal checks).
• Identify (in the description above) and document (add Asana tasks on this board) any technical debt that you're aware of, but are not addressing as part of this PR.

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🔍 Inspect: https://vercel.com/hashicorp/react-components/AFQUnqxY8VUAr1gBVQ72U7AVqRJj
✅ Preview: https://react-components-git-nqsubnav-enable-hashicorp-logo-hashicorp.vercel.app

[changeset-bot]

🦋 Changeset detected

Latest commit: 2978c8b

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@hashicorp/react-subnav	Patch

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