Validating that langtag and text direction are used as expected

[afs]

Use case: check that there are no @en-rtl, or more generally, that language and text direction, if present, are consistent.

e.g. How to find all literals with text direction "rtl" are @urd (Urdu), and all @urd have no text direction or it is "rtl`.

Literals have sh:datatype, sh:pattern and sh:languageIn to access components; there doesn't seem to be an equivalent for text direction.