Documentation: Value should be Json.Encode.Value

[anup-the-magic]

Link Value to Json.Encode.Value and be explicit about what it is in documentation

[50kudos]

Actually, I could add more related thing. Or let me know if I misunderstood something.
According to http://package.elm-lang.org/packages/fbonetti/elm-phoenix-socket/2.2.0/Phoenix-Channel :

Value of any function that begins with on e.g. onClose, onError, onJoin and onJoinError should be the Json.Decode.Value type because the value comes from the outside world. I know that Json.Decode.Value is actually Json.Encode.Value under the hood, but it is confusing.