feat: Support integration with other Node application

[promethyttrium]

Expected Behavior

Instead of just being used as a CLI, make npm-add-dependencies reusable by making it a module that can used programmatically.

Actual Behavior

Cannot be called programmatically.

[arfeo]

Hello,

Could you, please, describe more thoroughly the use case you want the program to be used in? Thank you.

[promethyttrium]

Sure, for example, if I were to write something similar to create-react-app, I would want to programmatically add a set of dependencies from inside another node.js application.

Currently, I can't just require('add-dependencies') and call it to add modules because index.js export any methods. It assumes that I'll always use add-dependencies as a CLI tool. I was to use it just like any other node module.

[phyzical]

Ah yes i actually ran into this issue today trying to refactor my build script further,

i.e say i wanted to go
npm run saveDependencies
with the following script

    "saveDependencies": "node tasks/saveDependencies.js",

then i would expect to be able to do something like

const addDeps =  require('add-dependencies');
addDeps.setDev(true)
addDeps.setOverwrite(false)
addDeps.addPackage('packagename')
addDeps.addPackage('packagename2')
addDeps.addPackages(['packagename3','packagename4'])
addDeps.updatePackageJson()

or something like that.

the reason for me wanting this is simply due to the fact that package.json doesn't allow for multi lines

but this does change it from a cli only package

[phyzical]

#21