Interface IAsyncSweetAlertService: public instead of protected

[Jan Bensch]

Is your feature request related to a problem? Please describe.
Both public classes SweetAlertService and SweetAlertMixin implement the protected interface IAsyncSweetAlertService. For unit testing our razor component we use bUnit. A convinient possibility for simulate the confirming oder denying the SweetAlert popup could be using Moq. But mocking a protected or private interface is not supported.

Describe the solution you'd like
Change the access modifier of the interface IAsyncSweetAlertService to public, if there is no special reason for the interface to be protected.