chore: Add RTL, Storybook, eslint rules and AGENTS

.storybook/preview.tsx

@@ -0,0 +1,39 @@
+import { withThemeByClassName } from '@storybook/addon-themes';
+
+import type { Preview } from '@storybook/react';
+import '../src/global.css';
+
+const preview: Preview = {
+  parameters: {
+    controls: {
+      matchers: {
+        color: /(background|color)$/i,
+        date: /Date$/i,
+      },
+    },
+    backgrounds: {
+      default: 'light',
+      values: [
+        {
+          name: 'light',
+          value: '#ffffff',
+        },
+        {
+          name: 'dark',
+          value: '#0a0a0a',
+        },
+      ],
+    },
+  },
+  decorators: [
+    withThemeByClassName({
+      themes: {
+        light: '',
+        dark: 'dark',
+      },
+      defaultTheme: 'light',
+    }),
+  ],
+};
+
+export default preview;