(re)-enable custom args to pack, install, and run script commands

[boneskull]

With the addition of support for multiple package managers, we lost the ability to pass extra arguments into the "pack", "install", and "run scripts" steps.

While this may be too awkward to express on the CLI, I could see the pm option allowing not just an array of strings, but an object with the package manager ID as the key, and an {installArgs?: string[], packArgs?: string[], runScriptArgs?: string[]} as the value.

Low priority until someone actually needs it. Some portion of this may be worked around by using package-manager-specific config files.