Add worker command for Docker setups (#9)

lib/Travelynx/Command/worker.pm

+package Travelynx::Command::worker;
+use Mojo::Base 'Mojolicious::Command';
+use Mojo::IOLoop;
+
+has description =>
+  'travelynx background worker';
+
+has usage => sub { shift->extract_usage };
+
+sub run {
+	my ($self) = @_;
+
+	Mojo::IOLoop->recurring(180 => sub {
+		$self->app->start('work');
+	});
+
+	Mojo::IOLoop->recurring(3600 => sub {
+		$self->app->start('maintenance');
+	});
+
+	if (not Mojo::IOLoop->is_running) {
+		Mojo::IOLoop->start;
+	}
+}
+
+1;
+
+__END__
+
+=head1 SYNOPSIS
+
+  Usage: index.pl worker
+
+  Background worker for cron-less setups, e.g. Docker.
+
+  Calls "index.pl work" every 3 minutes and "index.pl maintenance" every 1 hour.