User facing information should be rdf:langString, not xsd:string

[pchampin]

5 properties in SAI have range xsd:string. All of them are use-facing information (such as application name and desctiption).

Therefore, from an accessibility point of view, it would be better to declare rdf:langString as the range of these properties. It requires language tagging, and hints at the fact that providing the information in multiple languages would be a good idea.

[elf-pavlik]

Thank you @pchampin we are going to adjust it according to your suggestion.

[srosset81]

Another good idea would be to add language map in the JSON-LD context, like it is done for ActivityStreams:

https://github.com/w3c/activitystreams/blob/6880c92381cd5e3518651a1135ed819ef4828368/ns/activitystreams.jsonld#L226-L230