Community page: new tagline and diversity statement

[LukasWallrich]

Updates content/about/community/people.md:

• Tagline replaced with "Embedding open, rigorous, and inclusive scholarship in research and education."
• Header statement (the Mozilla Manifesto paragraph) replaced with a three-paragraph statement on inclusive community, diversity of identity and experience, and epistemological/methodological pluralism.
• Numbers in the "We are comprised of…" sentence checked against the Milestones list on the landing page (content/home/5-achievements.md) — all current, so unchanged.

Closes #625

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[LukasWallrich]

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Deployed at: 2026-08-19 15:51:40 UTC
Staging URL: https://staging.forrt.org

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