feat(admin, admin-ui, medusa-js, medusa-react, medusa): Support Admin Extensions (#4761)

Co-authored-by: Rares Stefan <948623+StephixOne@users.noreply.github.com>
Co-authored-by: Oli Juhl <59018053+olivermrbl@users.noreply.github.com>

packages/medusa/src/commands/utils/resolve-admin-cli.ts

@@ -0,0 +1,20 @@
+import fs from "fs-extra"
+import path from "path"
+
+export function resolveAdminCLI(directory: string) {
+  const cli = path.join(
+    directory,
+    "node_modules",
+    "@medusajs",
+    "admin",
+    "bin",
+    "medusa-admin.js"
+  )
+
+  const binExists = fs.existsSync(cli)
+
+  return {
+    binExists,
+    cli,
+  }
+}