Add a Breadcrumbs component or it's hook

[johannchopin]

Hey everyone👋 First thanks for the work that you put on this project! It's really helpful.

Is your feature request related to a problem? Please describe.
I created this slidev template to present some courses. One thing that was missing was some kind of Breadcrumbs component:

Describe the solution you'd like
So within my theme I created the Breadcrumbs component. Under the hood, it's using the useBreadcrumbs hook that return the list of titles and their slide number.

It seems to work pretty well so far so I was thinking maybe it would nice to add this component or hook directly in the slidev codebase. The hook is handy to easily create a customized breadcrumbs.

The only issue is that you will need to use the less performant --per-slide parameter when exporting the pdf.

So what do you think?