typescript declarations not working correctly for derived stores.

[srsholmes]

In some cases when using a derived store, the types are reported incorrectly. The return value of the derived store in this case in is a generated sdk from a Graphql Schema using https://www.graphql-code-generator.com.

As you can see, the method on the client has no declaration, jump to definition does not work, and as a result, the result from the method has no types. There are also no type errors for the input to the method.

This all works fine in VScode.

In VScode:

In Webstorm:

[tomblachut]

Should be contained in WEB-58397 use the svelte language server.