[Improvement] add type definition files (#361)

types/dialog.d.ts

@@ -0,0 +1,20 @@
+export type DialogOptions = {
+  title?: string;
+  message?: string;
+  overlay?: boolean;
+  lockOnScroll?: boolean;
+  confirmButtonText?: string;
+  cancelButtonText?: string;
+  showConfirmButton?: boolean;
+  showCancelButton?: boolean;
+  closeOnClickOverlay?: boolean;
+}
+
+export interface Dialog {
+  (options: DialogOptions): Promise<any>;
+  alert(options: DialogOptions): Promise<any>;
+  confirm(options: DialogOptions): Promise<any>;
+  close(): void;
+}
+
+export const Dialog: Dialog;