Disallow multiple modals of the same Type

[OpenEnergyGroup]

Is your feature request related to a problem? Please describe.
In Blazor Server, where there might be some milliseconds before the response makes it way back to the client, I've observed that a modal can be opened twice inadvertently, essentially by repeatedly hitting the button before the overlay is present. You can then end up with multiple identical modals stacked on top of each other.

Describe the solution you'd like
Something in the options to only allow a single instance of ComponentType. While multiple-modal functionality is desirable, it's unlikely you'd want multiple modals of the same modal. The service keeps track of open modal instances I believe, so a check before opening that there isn't already a modal opened (or opening).

Thank you.