BreadcrumbList schema validation issue

The BreadcrumbList implementation in baseof.html causes schema validation errors as it doesn't align with the schema at https://www.schema.org/BreadcrumbList. This can be seen when validating the site at https://search.google.com/test/rich-results. I have confirmed the exampleSite also fails similarly. I have overridden baseof.html on my site with the following changes to the BreadcrumbList, and have verified the issue goes away. ``` <ul vocab="https://schema.org/" typeof="BreadcrumbList"> {{ range $index, $element := .Site.Params.navlinks }} <li property="itemListElement" typeof="ListItem"> <a property="item" typeof="WebPage" href="{{ absURL $element.url }}"> <span property="name">{{ .name }}</span></a> <meta property="position" content="{{ add $index 1}}" /> </li> {{ end }} </ul> ``` Iam happy to create a PR if this helps. In addition, it will be useful if we could add the navigation bar to a partial.