add simple admin service

local-admin/public/src/shared/lib/markdown/normalizeAssetUrl.js

@@ -0,0 +1,9 @@
+export function normalizeAssetUrl(url) {
+  const normalized = url.trim();
+
+  if (/^(https?:|\/|#)/i.test(normalized)) {
+    return normalized;
+  }
+
+  return null;
+}