Support package alias

[mrdulin]

npm install <alias>@npm:<name>

Install a package under a custom alias.

My packages:

"antd": "^3.26.20",
"antd-v4": "npm:antd@^4.22.3",
"antd-v5": "npm:antd@^5.0.5",

$ npm-check -u

 Major Update Potentially breaking API changes. Use caution.
 ◯ @ant-design/icons                        4.8.0    ❯  5.0.1    https://github.com/ant-
design/ant-design-icons/tree/master#readme
 ◯ antd                                     3.26.20  ❯  5.2.1    https://ant.design
❯◯ react                                    16.14.0  ❯  18.2.0   https://reactjs.org/

As you can see, only the antd package is on the list, antd-v4 and antd-v5 are not on the list.

$ npm-check --version
6.0.1