docs: blog + community + dogfood docs should use .mdx extension

[slorber]

Follow-up of #8490

[netlify]

✅ [V2]

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[github-actions]

⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	PWA	Report
/	🟢 95	🟢 97	🟢 100	🟢 100	🟢 90	Report
/docs/installation	🟠 78	🟢 100	🟢 100	🟢 100	🟢 90	Report

[github-actions]

Size Change: +77 B (0%)

Total Size: 889 kB

Filename	Size	Change
website/build/assets/js/main.********.js	665 kB	+77 B (0%)

ℹ️ View Unchanged

Filename	Size
website/.docusaurus/globalData.json	71 kB
website/build/assets/css/styles.********.css	112 kB
website/build/index.html	40.9 kB

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