Documentation missing how to import core constants

[vladaman]

I am missing doc example how to import constants from core module:

const { subscriptionStatus, planInterval, planCurrency, churnType } = require('profitwell');
console.log(subscriptionStatus); // undefined

[edelciomolina]

Until a good soul makes a pull request 😄 ...

const { subscriptionStatus, planInterval, planCurrency, churnType } = require('profitwell/src/core');