fix: fix `<em>` styling

[piggynl]

This PR fixes <em> styling in some modern browsers.

Some links:

• https://caniuse.com/text-emphasis
• https://developer.mozilla.org/en-US/docs/Web/CSS/text-emphasis
• https://developer.mozilla.org/en-US/docs/Web/CSS/text-emphasis-position

[vercel[bot]]

This pull request is being automatically deployed with Vercel (learn more).
To see the status of your deployment, click below or on the icon next to each commit.

🔍 Inspect: https://vercel.com/sivan/heti/3Ymjd9mnybCRSQefQ93bYSEtk9MH
✅ Preview: https://heti-git-fork-piggynl-patch-1-sivan.vercel.app

[sivan]

This PR fixes \<em\> styling in some modern browsers.

Some links:

• https://caniuse.com/text-emphasis
• https://developer.mozilla.org/en-US/docs/Web/CSS/text-emphasis
• https://developer.mozilla.org/en-US/docs/Web/CSS/text-emphasis-position

@piggynl 最好调一下vendor-prefix的顺序～ https://stackoverflow.com/a/7080674

[piggynl]

Hi @sivan, 已经调好了~

[sivan]

谢谢，已经merge 🙏