[web-annotation] Issue: Base direction for annotations marked as editor_action

iherman has just labeled an issue for 
https://github.com/w3c/web-annotation as "editor_action":

== Base direction for annotations ==
[raised by r12a, not yet discussed by i18n WG]

In addition to language information, each annotation may need an 
optional indicator of overall base direction.

For example, the following annotation will not display correctly 
unless the application doing the display knows that the base direction
 needs to be rtl.  (As it is, the 'W3C' will appear to the right, as 
shown here, rather than to the left of the Hebrew.) 

```
{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno5",
  "type":"Annotation",
  "body": {
    "type" : "TextualBody",
    "text" : "<p>פעילות הבינאום, W3C</p>",
    "format" : "text/html",
    "language" : "en"
    "direction" : "rtl"
  },
  "target": "http://example.org/photo1"
}
``` 


See https://github.com/w3c/web-annotation/issues/224