Create `man` page utilizing `clap-mangen`

[BassedWarrior]

Create a man page for cppargo to be able to better explain the
functionallity of the application. This is a very useful resource, if only a
glorified help message at times. But still good to have none the less.

[BassedWarrior]

Moved to Backlog because man pages are mostly required for packaging purposes,
and since I have currently not made any binaries available either through the
GitHub releases or any sort of distro packaging, this is not currently a priority.