Missing links in doc

Those links are missing in latest documentation:

![Image](https://github.com/user-attachments/assets/8282f9ce-1f79-41ce-bb8a-a7d2467766e9)

We need to parse the mdx file and extract the `h2` and `<MemberLabel>` data.

The `links` from this file are missing: https://github.com/immutable-js/immutable-js/blob/265a9417a8e78f40561e3a0297b6924cf938fd1d/website/src/Sidebar.tsx#L31