add audio and video to generic context

Author: sanuann

reproschema/tests/contexts/generic

@@ -20,6 +20,14 @@
  "@id": "schema:image",
  "@type": "@id"
  },
+ "audio": {
+ "@id": "schema:audio",
+ "@type": "@id"
+ },
+ "video": {
+ "@id": "schema:video",
+ "@type": "@id"
+ },
  "inLanguage": {
  "@id": "schema:inLanguage"
  },