Migrate Documentation to Read the Docs

[harryswift01]

Currently, the prepmd documentation is mainly contained in the README.md. As the project is now maturing, it would be useful to move the longer documentation into a standard Read the Docs setup.

This would make the documentation easier to navigate, maintain, and keep consistent with other projects in the organisation.

Suggested changes:

• Add a docs/ directory.
• Move detailed usage and installation guidance from the README into Read the Docs.
• Keep the README as a short project overview with a link to the full documentation.
• Add the required Read the Docs configuration.

This would help make the project documentation more accessible and easier to maintain long term.