chore: update yarn.lock

Author: Guillaume Chau

package.json

@@ -73,6 +73,7 @@
     "@babel/core": "^7.0.0",
     "@babel/preset-env": "^7.0.0",
     "babel-core": "7.0.0-bridge.0",
+    "ps-tree": "^1.1.1",
     "vue": "2.5.17",
     "vue-template-compiler": "2.5.17",
     "vue-server-renderer": "2.5.17"