[Feature Request]: Add preview hovercards for internal links

### Prerequisites

- [x] I have searched existing issues to ensure this feature hasn't already been requested
- [x] I have tested using the latest version of docs-builder

### What problem are you trying to solve?

GitHub's documentation show hovercards with a preview of internal links when hovering over an internal docs link. The preview looks as follows:

I think we should add this to our docs, too.

### Proposed Solution

We could generate a page-metadata.json file at build that we could then access/read through the hovercard JS code. The JSON file would map links to their metadata.

### Examples and Research

GH seems to use an API for this, with calls to https://docs.github.com/api/article/meta?pathname=