docs: migrate UI docs (#13245)

* docs: create a new UI docs project (#13233)

* docs: create a new UI docs project

* fix installation errors

* docs: migrate UI docs content to new project (#13241)

* Fix content

* added examples for some components

* finish adding examples

* lint fix

* fix build errors

* delete empty files

* path fixes + refactor

* fix build error

www/apps/ui/specs/examples/select-controlled.tsx

@@ -0,0 +1,38 @@
+import { Select } from "@medusajs/ui"
+import * as React from "react"
+
+export default function SelectDemo() {
+  const [value, setValue] = React.useState<string | undefined>()
+
+  return (
+    <div className="w-[256px]">
+      <Select onValueChange={setValue} value={value}>
+        <Select.Trigger>
+          <Select.Value placeholder="Select a currency" />
+        </Select.Trigger>
+        <Select.Content>
+          {currencies.map((item) => (
+            <Select.Item key={item.value} value={item.value}>
+              {item.label}
+            </Select.Item>
+          ))}
+        </Select.Content>
+      </Select>
+    </div>
+  )
+}
+
+const currencies = [
+  {
+    value: "eur",
+    label: "EUR",
+  },
+  {
+    value: "usd",
+    label: "USD",
+  },
+  {
+    value: "dkk",
+    label: "DKK",
+  },
+]