feat: allow specifying custom target for FooterLogo

[vannyle]

Pre-flight checklist

• I have read the Contributing Guidelines on pull requests.
• If this is a code change: I have written unit tests and/or added dogfooding pages to fully verify the new behavior.
• If this is a new API or substantial change: the PR has an accompanying issue (closes #0000) and the maintainers have approved on my working plan.

Motivation

In the current documentation, it says Customization of the logo object. See Navbar logo for details, but it's not allowed to add a footer logo target.
This issue has been raised before in this PR #2344, it's available to specify a target only for the navbar logo.
It would be great if it works for the footer logo as well.

Test Plan

• Set the external link for the footer.logo.href property, and set the footer.logo.target property to "_self" - make sure that the external link opens in the current tab. This use case is the main goal of PR.

Test links

Deploy preview: https://deploy-preview-_____--docusaurus-2.netlify.app/

Related issues/PRs

• feat(v2): allow specifying custom target for logo link #2344

[Josh-Cena]

Nice work, very timely PR 😄

[netlify]

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[github-actions]

⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	PWA	Report
/	🟠 85	🟢 100	🟢 100	🟢 100	🟢 90	Report
/docs/installation	🟠 80	🟢 99	🟢 100	🟢 100	🟢 90	Report

[slorber]

Thanks 👍 LGTM