Update dependency prettier to v1.19.1

Author: renovate-bot

package.json

@@ -52,7 +52,7 @@
     "jest": "24.9.0",
     "lint-staged": "9.3.0",
     "nock": "11.3.5",
-    "prettier": "1.18.2"
+    "prettier": "1.19.1"
   },
   "scripts": {
     "build": "del index.js && babel index.mjs --out-dir .",