No go to reference for exceptions

Nobody has claimed this yet.

```reason
/* Example */
switch (result |> dataGet |> Json.Decode.list(Decode.repoProject)) {
| data => data
| exception (Json.Decode.DecodeError(msg)) =>
Js.log(msg);
[];
}
```

While hovering over / F12 over the symbol `DecodeError`, rls seems to not be able to tell that it is indeed exposed by the module `Json.Decode`, which is [defined here](https://github.com/glennsl/bs-json/blob/d545caf5547a0eef6b31812aa4c69ef3a5a882c8/src/Json_decode.mli#L16).

Start with the Reason example and the Json.Decode.DecodeError symbol, then inspect the declaration in Json_decode.mli at the linked line. Reproduce hover or F12 on DecodeError; the issue is done when the language server resolves it to the declaration exposed by Json.Decode.

Written by the indexing model from the issue text.