What problem does this feature solve?

I'm building docs for my language's std library, I hope to customize the outline item label, for example, I hope to show func() instead func(arg1: type1, arg2: type2).

We should extend the customizability beside to the anchor id.

https://rspress.dev/guide/basic/use-mdx#customizing-anchor-id

What does the proposed API look like?

None