Update preloaded JSON-LD (#7521)

src/remote/activitypub/misc/contexts.ts

@@ -511,6 +511,10 @@ const activitystreams = {
     "shares": {
       "@id": "as:shares",
       "@type": "@id"
+    },
+    "alsoKnownAs": {
+      "@id": "as:alsoKnownAs",
+      "@type": "@id"
     }
   }
 };