Use parent realm's copy of rubico for the code runners

At the moment, it's fetching every run and the examples are sometimes loading slowly. I've noticed on a fresh cache it was the first run that was slow and subsequent runs for different examples were quicker. Perhaps some caching is being done in the browser to that end. The relevant file should be `/CodeRunner.js`.

Note: Might have to perform a light refactor of the code runners to Realms first

The issue mentions performance improvements for code runners in the documentation site, specifically loading rubico from a parent realm to avoid repeated fetching. Start by examining `/CodeRunner.js` to understand the current implementation. Look for how rubico is loaded and where caching might be occurring. The goal is to refactor to use a shared copy, which may involve understanding Realms and the module structure.

Written by the indexing model from the issue text.