Added empty(obj, path) that also checks for object and arrays

[ggedde]

Added a simple method for checking whether the value is empty, but it also checks if the value is an object or array and if so checks if it has a .length

This makes for cleaner code:
Instead of:

const addOns = dotProp.get(data, 'cart.add_ons');
if( addOns && typeof addOns === 'object' && Object.keys(addOns).length) {
    // ...
}

You can now do:

if( !dotProp.empty(data, 'cart.add_ons')) {
    // ...
}

[sindresorhus]

I appreciate the PR, but this is not something I want in this package.