add stripe subscription node code example

Example 1: create a customer in stripe node.js

const stripe = require('stripe')('api_key');

stripe.customers.create({ email: 'email_address' }, (error, customer) => {
	if (error) {
      console.error(error);
    } else {
      console.log(customer);
    }
});

Example 2: stripe subscription node js

var stripe = require('stripe')('sk_test_FceQdct2QZpFfQZC4Wx9hGeo00ghaTeqAc');

stripe.subscriptions.create(
  {
    customer: 'cus_HKZRMeUnGPOb66',
    items: [{price: 'gold'}],
  },
  function(err, subscription) {
    // asynchronously called
  }
);