fix typescript warning

src/utils/Toast.ts

@@ -133,7 +133,7 @@ export class Toast {
       Toast._toasts[toastIndex].dismiss();
     }
   }
-  static _createContainer() {
+  static _createContainer(): void {
     const container = document.createElement("div");
     container.setAttribute("id", "toast-container");
     document.body.appendChild(container);