Update returrn type for `Plugin_2.loadData`

Currently, loadData returns Promise<any>.

It might help devs understand what’s going on better by giving it a more specific return type. Maybe something like:

loadData(): Promise<Record<string, unknown>>;

or even better (since someone might be storing arrays):

loadData<T>(): Promise<T>;

I think that will also prevent people from adding const settings = (await loadData()) || new MyPluginSettings().