feat: make code block titles clickable links

## Summary

When using code blocks with a `title` attribute that contains a URL, it would be nice if the title was rendered as a clickable link.

Currently:
```bash title="https://github.com/dwmkerr/dotfiles/blob/main/shell.functions.d/sourceenv.sh"
```

The title shows as plain text, but ideally it would be a clickable link to the source file.

## Options

1. **Swizzle the CodeBlock component** - customize how titles render, detect URLs and make them links
2. **Custom wrapper component** - create a `` component

## Context

Came up when creating the `sourceenv` snippet page - wanted to link to the source file in dotfiles.