Added [[+position]] placeholder to support schema.org/BreadcrumbList

[watou]

In schema.org/BreadcrumbList, each element in the breadcrumb list has the required property position, to indicate the depth of the item in the breadcrumb list. Example:

<ol itemscope itemtype="http://schema.org/BreadcrumbList">
  <li itemprop="itemListElement" itemscope
      itemtype="http://schema.org/ListItem">
    <a itemprop="item" href="https://example.com/dresses">
    <span itemprop="name">Dresses</span></a>
    <meta itemprop="position" content="1" />
  </li>
  <li itemprop="itemListElement" itemscope
      itemtype="http://schema.org/ListItem">
    <a itemprop="item" href="https://example.com/dresses/real">
    <span itemprop="name">Real Dresses</span></a>
    <meta itemprop="position" content="2" />
  </li>
</ol>

The MODX addon does not support this without adding the [[+position]] placeholder (this PR). The docs etc. would have to be updated as well.

Signed-off-by: John Cocula [email protected]

[JoshuaLuckers]

@benjamin-vauchel do you still maintain this extra? If not, would you mind if someone else adopts it?

[JoshuaLuckers]

@benjamin-vauchel I merged your PR in my own fork and released it as an update for the BreadCrumbs extra! 👍