Add 'gen' command to 'dancer2' runs

[stevieb9]

Per this thread on Perlmonks, the tutorial and manual were lacking the gen command in the dancer2 application examples:

Successfully installed Dancer2-0.400000 (upgraded from 0.301004)
1 distribution installed

steve@maezi ~/scratch >dancer2 -a

Unknown option: a
Usage: dancer2 [-h] -h --help --man [subcommand] at /Users/steve/perl5/perlbrew/perls/perl-5.32.1/lib/site_perl/5.32.1/CLI/Osprey/Descriptive/Usage.pm line 329.

[cromedome]

👍 Thank you!