add library install in composer.json

It's recommended to use asset-packagist to install JavaScript libraries. Like bower-asset or npm-asset
Add the following to your composer.json file into the repositories section:

 {
        "type": "composer",
        "url": "https://asset-packagist.org"
    }

And extend the 'installer-path' section:

"web/libraries/{$name}": [
        "type:drupal-library",
        "type:bower-asset",
        "type:npm-asset"
    ],

And add a new 'installer-types' section next to the 'installer-path' in the 'extra' section:
"installer-types": ["bower-asset", "npm-asset"],

It need to add more details to comment #2 ✨ add library install in composer.json Active and to the documentation of module:

composer require oomphinc/composer-installers-extender
// All actions as commented in #2
composer require bower-asset/bootstrap-datepicker