Add structured data

[masakudamatsu]

Reference: https://www.evernote.com/l/AFPI5kDrCltPz5sUt9cFPQHCSEVNCzCEtTg

[masakudamatsu]

We add the following in the element of index.html:

• The JSON-LD can be inserted either in the or . See https://www.youtube.com/watch?v=lI6EtxjoyDU

    <script type="application/ld+json">
      {
        "@context": "http://schema.org",
        "@type": "WebApplication",
        "name": "Line-height Picker",
        "url": "",
        "applicationCategory": "Developer tools",
        "genre": "typography",
        "browserRequirements": "Requires JavaScript. Requires HTML5.",
        "softwareVersion": "1.0.0",
        "operatingSystem": "All"
        "offers": {
          "@type": "Offer",
          "price": "0"
        }
    }
    </script>

• The name and `offers.price' property is required for softwareApplication: https://developers.google.com/search/docs/data-types/software-app
• The aggregateRating or review is also required, but obviously we don't have one.
• The applicationCategory and operatingSystem are recommended: https://developers.google.com/search/docs/data-types/software-app
• The value for applicationCategory follows the categories for Apple App Store and Microsoft App Store.
• The rest follows an example in https://www.darrenlester.com/blog/json-ld-structured-data-for-web-applications
• The description property is omitted. It's a duplicate with the meta tag (#5). It's unlikely to be updated together with the meta tag description. I guess that will do more harm than good.

[masakudamatsu]

Filling the 'url' property value is delegated to issue #221

[masakudamatsu]

For author information, we just use rel="author" in the link tag for my Twitter account in the Footer section.