refactor: change string to constants

Refs: #649 (comment)

frontend/src/components/Modal/ApplicationPreviewModalWindow/ApplicationPreviewModalWindow.stories.tsx

@@ -1,6 +1,6 @@
 import { ComponentMeta, ComponentStory } from "@storybook/react";
 import useModalContext from "../../../hooks/useModalContext";
-import Button from "../../@common/Button/Button";
+import Button, { BUTTON_VARIANT } from "../../@common/Button/Button";
 import ApplicationPreviewModalWindow from "./ApplicationPreviewModalWindow";
 
 export default {
@@ -13,7 +13,13 @@ const Template: ComponentStory<typeof ApplicationPreviewModalWindow> = (args) =>
 
   return (
     <div style={{ height: "200vh", backgroundColor: "white", padding: "1rem" }}>
-      <Button type="button" variant="contained" cancel={false} className onClick={openModal}>
+      <Button
+        type="button"
+        variant={BUTTON_VARIANT.CONTAINED}
+        cancel={false}
+        className
+        onClick={openModal}
+      >
         open modal
       </Button>
       <Modal>