Add optional breadcrumb trail

[h-enk]

Set in ./config/_default/params.toml:

[options]
  breadCrumb = true

Example:

Markup:

<nav aria-label="breadcrumb">
  <ol class="breadcrumb">
    <li class="breadcrumb-item"><a href="//localhost:1313/">Home</a></li>
    <li class="breadcrumb-item"><a href="//localhost:1313/docs/">Docs</a></li>
    <li class="breadcrumb-item"><a href="//localhost:1313/docs/prologue/">Prologue</a></li>
    <li class="breadcrumb-item active" aria-current="page">Introduction</li>
  </ol>
</nav>

Note: this is an optional user breadcrumb trail — next to the already implemented JSON-LD for rich results:

{
  "@context":"http://schema.org",
  "@type":"BreadcrumbList",
  "itemListElement":[
    {
      "@type":"ListItem",
      "position":1,
      "name":"Home",
      "item":"https:\/\/getdoks.org"
    },
    {
      "@type":"ListItem",
      "position":3,
      "name":"Docs",
      "item":"https:\/\/getdoks.org\/docs\/"
    },
    {
      "@type":"ListItem",
      "position":4,
      "name":"Prologue",
      "item":"https:\/\/getdoks.org\/docs\/prologue\/"
    },
    {
      "@type":"ListItem",
      "position":5,
      "name":"Introduction",
      "item":"https:\/\/getdoks.org\/docs\/prologue\/introduction\/"
    }
  ]
}

[h-enk]

https://doks-breadcrumb-navigation--doks.netlify.app/