Add validator schema for breadcrumbs and slider

[pkarw]

Under src/resource there are some json files to be used across app. Only order has it own validation schema under src/models

It's more for documentation purposes for now and to keep models logic coherent

We're using Ajv validator (take a look at store/modules/checkout.js):

const Ajv = require('ajv') // json validator
    const ajv = new Ajv()
    const validate = ajv.compile(require('../../models/order_schema.json'))

More on that: https://github.com/epoberezkin/ajv