This makes it easier to add new dependencies, without having to
manually edit the `aiken.toml` file.
The command is accessible via two different paths:
- aiken deps add
or simply
- aiken add
for this is quite common to find at the top-level of the command-line,
and, we still want to keep commands for managing dependencies grouped
under a command sub-group and not all at the top-level. So we're
merely promoting that one for visibility.
38df9a586e