[fix] duniter-ui commands won't start without this dependency

package.json

@@ -57,6 +57,7 @@
     "request": "2.81.0",
     "request-promise": "4.2.0",
     "sha1": "1.1.1",
+    "spawn-sync": "^1.0.15",
     "sqlite3": "3.1.4",
     "superagent": "3.5.2",
     "tail": "^1.2.1",