Document the functionality of the tool properly

[ionut-arm]

The functionality of the Parsec tool (commands, options...) is available as part of the binary itself, generated by clap, but no proper external documentation exists. This page documents the process of rendering such documentation as a manpage for a Rust CLI app. The linked discussion points to clap-mangen as the tool to use for this purpose.

Another important factor would be to provide some example scripts for how to achieve various goals, in a markdown page.

Once such documentation is available, the Parsec book (in particular this page) should be enhanced with information about the manpage and the examples.