-www option ignored

# Bug Report

## Problem

### What is expected to happen?
When the `-www` option is used, plugins should be installed in the given directory instead of the default `/cordova/plugins`

### What does actually happen?
Plugins are still installed in the default directory.

## Information

### Command or Code

% ls
www myproj

% plugman install --platform ios --proj myproj --plugin cordova-plugin-device --www ./www
% plugman install --platform ios --proj myproj --plugin cordova-plugin-device --www .
% plugman install --platform ios --proj myproj --plugin cordova-plugin-device --www www

Plugins are installed in myproj/cordova/plugins, instead of the local www directory

### Environment, Platform, Device

Using platofrm-ios directly, no cordova CLI. Happens with every plugin.

### Version information

plugman 3.0.1
cordova-ios 6.2.0
npm 7.20.3
node 16.7.0
macOS 11.6

## Checklist
- [x] I searched for existing GitHub issues
- [x] I updated all Cordova tooling to most recent version
- [x] I included all the necessary information above

Start with the plugman install command and reproduce the reported cases using --platform ios, --proj myproj, --plugin cordova-plugin-device, and each --www value. Trace how the --www option is handled and verify that plugins are installed in the requested local directory rather than myproj/cordova/plugins.

Written by the indexing model from the issue text.