Add remote file support to includes shortcode

[jtracey93]

This pull request introduces a new shortcode template in the docs/layouts/shortcodes/include.html file to handle the inclusion of external resources and files with various options for rendering content.

Key changes:

• Added variables to capture parameters for URL
• Implemented logic to fetch and render content based on the provided URL or file, with support for syntax highlighting, HTML rendering, and page content inclusion.

Testing evidence