An array of type indicators. A type indicator provides semantic information for
the object in context. It is very similar to the rel attribute of h:link,
but h:link.rel indicates semantics of the linked element, whereas h:type indicates
semantics of the object in the context.
Just like in the case of rel you SHOULD only use standard types as simple
strings, all custom types should be indicated as CURIEd URIs. The order of
these types should not be considered signficant.