Schema Markup Validator for RDFa is tripped up by rel="external" on an anchor

**The property external is not recognized by the schema (e.g. schema.org) for an object of type Person.**
```
<section vocab="https://schema.org/" typeof="Person">
<a rel="external" href=""></a>
</section>
```
 V29.1 | 2025-04-24