Update dependency prettier to v1.19.0

Author: renovate-bot

package-lock.json

@@ -38,7 +38,7 @@
     "mocha": "6.2.2",
     "npm-run-all": "4.1.5",
     "phantomjs-prebuilt": "2.1.16",
-    "prettier": "1.18.2",
+    "prettier": "1.19.0",
     "rollup": "1.26.3",
     "rollup-plugin-commonjs": "10.1.0",
     "rollup-plugin-json": "4.0.0",