Add prevRecURI.

Fixes w3c/json-ld-wd#22.

Author: gkellogg

index.html

@@ -27,6 +27,7 @@
       prevVersion:            "https://www.w3.org/TR/2018/WD-json-ld11-20181011/",
       previousPublishDate:    "2018-10-11",
       previousMaturity:       "WD",
+      prevRecURI:             "https://www.w3.org/TR/2014/REC-json-ld-20140116/",
       github:                 "https://github.com/w3c/json-ld-syntax/",
 
       // if there a publicly available Editor's Draft, this is the link