chore: fix iframe background color in dark mode

[lex111]

Motivation

It turns out that using color-scheme can lead to incorrect backgrounds in iframes on dark scheme. At least on our site:

Not sure if we should globally assign color-scheme to auto to avoid this issues on our client sites?

Have you read the Contributing Guidelines on pull requests?

Yes

Test Plan

Related PRs

(If this PR adds or changes functionality, please take some time to update the docs at https://github.com/facebook/docusaurus, and link to your PR here.)

[netlify]

✔️ [V2]

🔨 Explore the source changes: 9a83428

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[github-actions]

⚡️ Lighthouse report for the changes in this PR:

Category	Score
🟢 Performance	98
🟢 Accessibility	98
🟢 Best practices	100
🟢 SEO	100
🟢 PWA	95

Lighthouse ran on https://deploy-preview-5223--docusaurus-2.netlify.app/

[github-actions]

Size Change: +30 B (0%)

Total Size: 856 kB

Filename	Size	Change
website/build/assets/css/styles.********.css	92 kB	+36 B (0%)

ℹ️ View Unchanged

Filename	Size	Change
website/.docusaurus/globalData.json	59.2 kB	0 B
website/build/assets/js/main.********.js	461 kB	0 B
website/build/blog/2017/12/14/introducing-docusaurus/index.html	62.4 kB	0 B
website/build/blog/index.html	26.4 kB	0 B
website/build/docs/index.html	40.3 kB	-3 B (0%)
website/build/docs/installation/index.html	47.9 kB	-3 B (0%)
website/build/index.html	27.3 kB	0 B
website/build/tests/docs/index.html	20.9 kB	0 B
website/build/tests/docs/standalone/index.html	18.8 kB	0 B

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[slorber]

thanks

this is a bit weird, surprised by this behavior 😅

Not sure if we should globally assign color-scheme to auto to avoid these issues on our client sites?

yeah applying this for all iframes in Infima can make sense, maybe we'll see according to user feedbacks after the release?

[lex111]

yeah applying this for all iframes in Infima can make sense, maybe we'll see according to user feedbacks after the release?

Yes, I think it's safe to do for all iframes. Perhaps our users who used iframes also like us until today did not know about this small BC.