AP: Recognize "CryptographicKey" as a type of http sig keys

The examples in the security vocabulary's spec use "Key" but the JSON-LD
context doesn't define that term. From now on, just in case, recognizing both
"Key" and "CryptographicKey" as indication that the object is a key.

zPlus, thanks for finding this bug!

src/Web/ActivityPub.hs

@@ -223,8 +223,8 @@ instance ActivityPub PublicKey where
     parseObject o = do
         mtyp <- optional $ o .: "@type" <|> o .: "type"
         for_ mtyp $ \ t ->
-            when (t /= ("Key" :: Text)) $
-                fail "PublicKey @type isn't Key"
+            unless (t == ("Key" :: Text) || t == "CryptographicKey") $
+                fail "PublicKey @type isn't Key or CryptographicKey"
         RefURI authority id_ <- o .: "@id" <|> o .: "id"
         shared <- o .:|? "isShared" .!= False
         fmap (authority,) $