fix a11y on home: one h1 and named partner links

[angelabenavente]

This pull implements some accessibility fixes on Home.

SUMMARY

Section titles used h1 + h3, and the bottom CTA was another h1, so the page had several top-level headings.
Partner wordmarks are inline SVGs inside links with no text, so Lighthouse flagged empty links.

FIXES

• SectionTitle has now h2 + p nodes.
• CTA heading is h2 nodes.
• Partner links now have aria-label;

AUDITED RESULT

Lighthouse Accessibility on the homepage: 93 → 97.

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Screenshots

Headings (before) — several h1 on https://reactnative.dev/

Headings (after) — one h1 (“React Native” title on hero)

Partner links (before) — empty names in Lighthouse

Partner links (after) — aria-label on each company link

Lighthouse (before) — 93

Lighthouse (after) — 97

[Simek]

Hey @angelabenavente, thanks for improving the home page a11y! 👍

Tested the changes on PR - https://deploy-preview-5222--react-native.netlify.app/

LGTM 🚀