Update elm.json in subscriptions example.

Author: dillonkearns

examples/subscription/elm.json

@@ -17,6 +17,7 @@
             "elm/time": "1.0.0",
             "elm/url": "1.0.0",
             "elm-community/list-extra": "8.0.0",
+            "j-maas/elm-ordered-containers": "1.0.0",
             "krisajenkins/remotedata": "6.0.1",
             "lukewestby/elm-string-interpolate": "1.0.4",
             "mdgriffith/elm-ui": "1.1.0",