docs(gh-docs): Rename Facebook to Meta in GitHub-related Markdowns

[raghav2005]

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

Facebook is officially called Meta now, so I thought it's worth changing the important Markdown documents to reflect this update - I didn't want to mess with the actual code too much as I'm not very experienced.

Test Plan

N/A

Test links

Deploy preview: https://deploy-preview-10566--docusaurus-2.netlify.app/

Related issues/PRs

N/A

[facebook-github-bot]

Hi @raghav2005!

Thank you for your pull request and welcome to our community.

Action Required

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Process

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[facebook-github-bot]

Thank you for signing our Contributor License Agreement. We can now accept your code for this (and any) Meta Open Source project. Thanks!

[github-actions]

⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	Report
/	🟠 69	🟢 98	🟢 96	🟢 100	Report
/docs/installation	🟠 53	🟢 97	🟢 100	🟢 100	Report
/docs/category/getting-started	🟠 74	🟢 100	🟢 100	🟠 86	Report
/blog	🟠 60	🟢 96	🟢 100	🟠 86	Report
/blog/preparing-your-site-for-docusaurus-v3	🔴 48	🟢 92	🟢 100	🟢 100	Report
/blog/tags/release	🟠 63	🟢 96	🟢 100	🟠 86	Report
/blog/tags	🟠 74	🟢 100	🟢 100	🟠 86	Report

[zpao]

I should update some of these with new language we have generally, but this is good as is. Thanks!