Improve user documentation

Description

The current documentation is rather limited for anyone wanting to use the read-to-use executables. It is also not completely clear how the configuration file or the parameter tree should look like.

Proposal

Include and extend pages to the docusaurus webpage.

How to test the implementation?

It deploys to Netlify successfully. (See https://dune-copasi.netlify.app/)

Related issues

See #27 (closed)