chore(v2): update Infima to alpha 28

[lex111]

Motivation

Includes styles for secondary mobile menu and admonitions changes.

Have you read the Contributing Guidelines on pull requests?

Yes

Test Plan

Preview

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: c25fa5d

🔍 Inspect the deploy log: https://app.netlify.com/sites/docusaurus-2/deploys/60fff392a01b77000741c306

😎 Browse the preview: https://deploy-preview-5222--docusaurus-2.netlify.app

[github-actions]

⚡️ Lighthouse report for the changes in this PR:

Category	Score
🟠 Performance	72
🟢 Accessibility	98
🟢 Best practices	100
🟢 SEO	100
🟢 PWA	95

Lighthouse ran on https://deploy-preview-5222--docusaurus-2.netlify.app/

[github-actions]

Size Change: -569 B (0%)

Total Size: 856 kB

Filename	Size	Change
website/build/assets/css/styles.********.css	91.4 kB	-563 B (-1%)

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

_{compressed-size-action}

[slorber]

LGTM 👍