[FEATURE REQUEST] To allow renaming field name

[motss]

This feature request might be useful for folks who need it:

const wl = require('whitelister');

const schema = {
  type: 'object',
  attributes: {
    first_name: { type: 'string', as: 'firstName' },
    last_name: { type: 'string', as: 'lastName' },
    type: { type: 'string', as: 'userType' },
  },
};
const data = {
  first_name: 'John',
  last_name: 'Doe',
  type: 'VIP',
};
const results = await wl(schema, data);
/**
 * {
 *   firstName: 'John'
 *   lastName: 'Doe',
 *   userType: 'VIP',
 * }
 */