fix(a11y): resolve axe color-contrast and accessible-name failure

[ryzrr]

Summary
Fixes the visual contrast of some text.

After

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Project	Deployment	Actions	Updated (UTC)
webpack-doc-kit	Ready	Preview, Comment	Jul 21, 2026 5:55pm

[github-actions]

⚡ Lighthouse report

Audited the Vercel preview deployment: https://webpack-doc-i2ax0gqf1-openjs.vercel.app

URL	Performance	Accessibility	Best Practices	SEO	Report
/	🟢 97	🟢 96	🟢 100	🟢 100	🔗
/about	🟢 99	🟢 97	🟢 100	🟢 100	🔗
/about/sponsors	🟢 99	🟢 95	🟢 96	🟢 100	🔗
/blog	🟢 99	🟢 96	🟢 100	🟢 100	🔗
/blog/posts/2026-02-04-roadmap-2026	🟢 99	🟢 93	🟢 100	🟢 100	🔗
/guides/getting-started	🟢 96	🟢 97	🟢 100	🟢 100	🔗
/docs/api/v5.x/options	🔴 68	🟢 96	🟢 100	🟢 100	🔗
/docs/loaders/css-loader	🟢 99	🟢 97	🟢 100	🟠 83	🔗

Scores are advisory (warn at 90); they do not fail the build. See .lighthouserc.json.