Anchor links broken in docs.rascal-mpl.org

[DamDC91]

Describe the bug

Some anchor links aren't working on this page.

To Reproduce

Most of the links expect the ones in 1. Prelude are broken.

Example when clicking on concat:

https://docs.rascal-mpl.org/unstable/Libraries/#Libraries/Prelude/List-concat should be https://docs.rascal-mpl.org/unstable/Libraries/#List-concat

[jurgenvinju]

Thanks Dennis! Working on it with the documentation project @JJWTimmer