feat: invalidateQueryAndRefetchIfListeners()

[iOSonntag]

First of all great work!

Regarding my issue, I searched ages and dived deep into the framework code on how to be able to invalidate a query and only refetch it, if it actually is used somewhere. Turns out its not possible out of the box so I wrote myself an extension:

extension ExtensionOnQueryBase<T, State extends QueryState<dynamic>> on QueryBase<T, State> {

  void invalidateQueryAndRefetchIfListeners()
  {
    invalidateQuery();

    if (hasListener) refetch();
  }
}

I know the name is not the best, but explaining people that this is what you want regarding not asking the server to much and still having a nice user experience and it is not shipped within the docs or the framework might be an issue for many people beeing guided in the wrong driection IMO