Add documentation for Hugo shortcodes

[pierzchala-m]

Currently, there is no documentation describing the available Hugo shortcodes, their purpose, or how to use them. This makes it difficult for contributors and users to discover existing functionality and apply it correctly.

It would be helpful to have documentation that includes:

• A list of all supported shortcodes
• A brief description of what each shortcode does
• Usage examples (including parameters and defaults)
• Any constraints or caveats

Suggested locations could be the project README, a dedicated documentation page, or inline docs under layouts/shortcodes.

Adding this would significantly improve usability and reduce onboarding friction.

Expected outcome:

Clear, centralized documentation for all Hugo shortcodes used in the project.
If shortcodes are not used in the project, there should be a note, they can be delated.