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/text-weights.tsx

@@ -0,0 +1,10 @@
+import { Text } from "@medusajs/ui"
+
+export default function TextWeights() {
+  return (
+    <div className="flex flex-col gap-y-2">
+      <Text weight="regular">Regular weight</Text>
+      <Text weight="plus">Plus weight</Text>
+    </div>
+  )
+}