Use role="alert" rather than role="alertdialog"

dialogs/alertdialogs are intended to receive focus when they're shown. toasts, by their very nature, are not meant to steal focus but happen in parallel/as an aside

src/lib/toastr/toast.component.ts

@@ -25,10 +25,10 @@ import { ToastrService } from './toastr.service';
   <div *ngIf="title" [class]="options.titleClass" [attr.aria-label]="title">
     {{ title }} <ng-container *ngIf="duplicatesCount">[{{ duplicatesCount + 1 }}]</ng-container>
   </div>
-  <div *ngIf="message && options.enableHtml" role="alertdialog"
+  <div *ngIf="message && options.enableHtml" role="alert"
     [class]="options.messageClass" [innerHTML]="message">
   </div>
-  <div *ngIf="message && !options.enableHtml" role="alertdialog"
+  <div *ngIf="message && !options.enableHtml" role="alert"
     [class]="options.messageClass" [attr.aria-label]="message">
     {{ message }}
   </div>