feat(shadcn-ui): Setup shadcn-ui

What I did:

Run following shadcn-ui init command.

```bash
$ npx shadcn@latest init
# style -> Default
# base color -> Stone
# use CSS variables -> yes
```

Ref:
    https://ui.shadcn.com/docs/installation/vite

components.json

@@ -0,0 +1,20 @@
+{
+  "$schema": "https://ui.shadcn.com/schema.json",
+  "style": "default",
+  "rsc": false,
+  "tsx": true,
+  "tailwind": {
+    "config": "tailwind.config.js",
+    "css": "src/index.css",
+    "baseColor": "stone",
+    "cssVariables": true,
+    "prefix": ""
+  },
+  "aliases": {
+    "components": "@/components",
+    "utils": "@/lib/utils",
+    "ui": "@/components/ui",
+    "lib": "@/lib",
+    "hooks": "@/hooks"
+  }
+}