Resumable (tus) uploads don't emit upload, upload.error

[LauraTran]

To Reproduce

<vue-file-agent 
   :resumable="true" 
   :uploadUrl="'/some/tus/upload/endpoint/'"
  @upload="onUploadSuccess"
></vue-file-agent>

Expected behavior
Once the file uploads, the method onUploadSuccess should be called.
Currently it's not being called because the method upload just returns the result and does not emit the event as it does when resumable is false.