Update dependency start-server-and-test to v1.12.0

Author: renovate-bot

package-lock.json

@@ -76,7 +76,7 @@
     "npm": "6.14.8",
     "npm-run-all": "4.1.5",
     "prettier": "2.1.2",
-    "start-server-and-test": "1.11.5"
+    "start-server-and-test": "1.12.0"
   },
   "dependencies": {
     "gitbook-plugin-anchors": "^0.7.1",