feat(theme-classic): add social icons for mastodon and bluesky

[cemerick]

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.

Motivation

Allow blog authors to display mastodon & bluesky social icons without swizzling. Pre-PR discussion @ #10762

Note that this does not do anything fancy re: generating the actual social URL from anything shorter than an actual URL, since bluesky and mastodon profile links can have ~arbitrary domains, etc.

Test Plan

These are just icons, so no tests added here. Tweaks made to a dogfooding page and the authors file there to make sure the new icons show up. I also did do a sanity check with my own site. 👍

Test links

Deploy preview: https://deploy-preview-10764--docusaurus-2.netlify.app/tests/blog

[netlify]

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[github-actions]

⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	Report
/	🔴 40	🟢 98	🟢 96	🟢 100	Report
/docs/installation	🟠 50	🟢 97	🟢 100	🟢 100	Report
/docs/category/getting-started	🟠 74	🟢 100	🟢 100	🟠 86	Report
/blog	🟠 64	🟢 96	🟢 100	🟠 86	Report
/blog/preparing-your-site-for-docusaurus-v3	🔴 48	🟢 92	🟢 100	🟢 100	Report
/blog/tags/release	🟠 64	🟢 96	🟢 100	🟠 86	Report
/blog/tags	🟠 74	🟢 100	🟢 100	🟠 86	Report

[cemerick]

I see some "lint" failures, but it seems it's just complaining about unknown terms ("bluesky", etc). I was about to update project-words.txt (where it seems such things are enumerated), but it's apparently a CI-generated file?

Let me know if there's anything I should do here to address this.

[Josh-Cena]

You can run the command yarn lint:spelling:fix locally to update this file!

[cemerick]

You can run the command yarn lint:spelling:fix locally to update this file!

I've been incrementally resolving the problems reported by the linter(s), most recently prettier formatting. However, it looks like I've updated the PR more times than github likes before it's forcing a maintainer's approval to re-run those workflows again. 👉👈

[GingerGeek]

Hey @cemerick I see we both wanted the same thing 😅

I have a similar PR in #10768 which also includes link handling for new social sites as well the icon inclusion

[cemerick]

@GingerGeek You've got more (very reasonable IMO) social sites added, so I'm happy to have yours taken instead 👍