Rollout the design system on offline pages

[Andy-set-studio]

Fixes #6842

[chrome-devrel-review-bot]

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src/site/content/en/offline.md

• This file passed all of our automated Markdown audits.

src/site/content/es/offline.md

• This file passed all of our automated Markdown audits.

src/site/content/ja/offline.md

• This file passed all of our automated Markdown audits.

src/site/content/ko/offline.md

• This file passed all of our automated Markdown audits.

src/site/content/pl/offline.md

• This file passed all of our automated Markdown audits.

src/site/content/pt/offline.md

• This file passed all of our automated Markdown audits.

src/site/content/ru/offline.md

• This file passed all of our automated Markdown audits.

src/site/content/zh/offline.md

• This file passed all of our automated Markdown audits.

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