Currently the `notifyTesters` field in the `DistributeResourceTask` is hardcoded to `false` but could be easily set as a parameter when generating the `UploadTask`

Adding this will give developers control over whether the testers should be notified of the new release, rather than assuming that they always do not want to notify.

Acceptance Criteria:

1. Notify Testers can be specified in the configuration for the plugin.
2. Notify Testers is optional.
3. Notify Testers defaults to true.
4. A test is provided to assert the status of the flag in the uploaded JSON.