Add support for emojis in the sidebar

[Veetaha]

I tried to add this item to the sidebar to denote an experimental feature:

{
    text: "🔬 overwritable",
    link: "/reference/builder/member/overwritable",
}

but it rendered without the 🔬 symbol:

I think it makes sense to allow emojis there. This still looks nice (I just added this manually via dev tools for demo purposes):

[brc-dd]

Seems to work fine 👀

https://stackblitz.com/edit/vite-jn4gzs?file=docs/.vitepress/config.ts

[Veetaha]

Indeed, maybe I just didn't update the page :flushed:, I though I did, but now that I try it again I can't reproduce this. I'll close this issue, thanks!

[brc-dd]

I'm seeing some issues with restarting being unreliable. Probably something changed in newer vite versions. Tracking it along bun support in #4313