Add section on setting the text direction

[fsteeg]

For details see #126 (where each item links to the relevant part of the W3C i18n docs).

[wetneb]

Looks good to me. I wonder if we should add this field to the JSON schemas (and similarly the language field) or if it is just noise. Maybe it would be nice to have some examples use this (also to illustrate the inheritance described)?

[fsteeg]

Yes, not sure about the schemas too, we have lang in a sample and it validates. For dir in a manifest: we currently have real-world sample manifests, so it would be weird to add it to an existing, or making one up. The manifest schema does not forbid additionalProperties, so manifests with dir validate. I don't think the schemas need to be something like a full spec of whats allowed in an element.

For the full example of dir and inheritance, I did try to come up with something similar to the lang example, but could not find anything useful in our GND data (from what I understand, setting the base direction is required when mixing left-to-right and right-to-left strings). I tried constructing a data extension request against the Wikidata reconciliation endpoint (basically: give me the Persian label for 'Yahoo!'), but did not get that to work (the label itself is not a property? [1]). In the end I was happy with the little inline 'Yahoo!' example, in particular since the inheritance mechanism works just like lang, for which we have the full example.

[1] Tried smth. like this: https://wikidata.reconci.link/fa/api?extend={%22ids%22%3A[%22Q37093%22]%2C%22properties%22%3A[{%22id%22%3A%22P2561%22}]}

[fsteeg]

With help from @wetneb in today's meeting I was able to come up with an example in ea79f96 (based on a Wikidata extension query, which looks a bit different but would actually require setting a dir to render correctly).