Include Video data in import

Related to PR vue-storefront#2388 for adding support of videos in product gallery.
The following JSON is a sample of data coming from Magento 2 with 1 image, 1 YouTube video, and 1 Vimeo video. In order to use these in VS we need to include the extra data in the import.
[
    {
        "id": 3423,
        "media_type": "image",
        "label": null,
        "position": 1,
        "disabled": false,
        "types": [
            "image",
            "small_image",
            "thumbnail",
            "swatch_image"
        ],
        "file": "/s/h/shop_home_we_1.jpg"
    },
    {
        "id": 3431,
        "media_type": "external-video",
        "label": null,
        "position": 2,
        "disabled": false,
        "types": [],
        "file": "/h/q/hqdefault_1.jpg",
        "extension_attributes": {
            "video_content": {
                "media_type": "external-video",
                "video_provider": "",
                "video_url": "https://youtu.be/M7R0bQHilgw",
                "video_title": "Storefront Cloud - Technical Overview",
                "video_description": "Storefront Cloud is a Mobile-first eCommerce Platform that helps you build engaging user-experience across all platforms and devices. Get focus on client interactions without any changes on the backend.\r\n\r\n\r\nStorefront Cloud Platform combine features offered by most modern browsers with the benefits of the native mobile experience, to give your business a significant profits.\r\n\r\nPowered by:\r\n\r\nProgressive Web Apps (PWA) \r\nAccelerated Mobile Pages (AMP) \r\nOpen Loyalty Platform \r\n\r\n\r\nPWA is a Web application which behaves the same way like the native:\r\n\r\n- can be used without the internet connection,\r\n\r\n- like an app - is blazingly fast,\r\n\r\n- can be added to Home screen but without installation process,\r\n\r\n- in contrast to Apps is linkable - easy to share,\r\n\r\n- offers the same UX and UI like native apps, with push notifications etc.\r\n\r\n\r\nSo, our goal was to create Mobile-first, Offline-first eCommerce app which will be:\r\n\r\n- Fault tolerant - because it can work even without Internet access, it can run without any central servers - there is no such traffic peak that will kill the service,\r\n\r\n- We're to use all the PWA benefits - app manifest to install it on the home screen, use Service Workers to cache data etc. More on that later!\r\n\r\n- Would be great if we can achieve the response times within few dozen milliseconds per interaction,\r\n\r\n- The storefront is also designed to be platform agnostic - so to be able to integrate the same way with Magento, Pimcore, Shopify Plus or other platforms.\r\n\r\n\r\n\r\nFollow Storefront Cloud Online Here:\r\n\r\nWebsite: https://storefrontcloud.io\r\nCo-Founders:\r\nhttps://twitter.com/piotrkarwatka\r\nhttps://twitter.com/filrakowski",
                "video_metadata": ""
            }
        }
    },
    {
        "id": 3432,
        "media_type": "external-video",
        "label": null,
        "position": 3,
        "disabled": false,
        "types": [],
        "file": "/7/2/724617781_640.jpg",
        "extension_attributes": {
            "video_content": {
                "media_type": "external-video",
                "video_provider": "",
                "video_url": "https://vimeo.com/289059028",
                "video_title": "Vue Storefront 2.0",
                "video_description": "New Vue Storefront branding",
                "video_metadata": ""
            }
        }
    }
]
vuestorefront / mage2vuestorefront

Include Video data in import #71
