chore(package): update prettier to version 2.0.1

Closes #30

Author: greenkeeper[bot]

package.json

@@ -31,7 +31,7 @@
     "eslint-config-prettier": "6.0.0",
     "esm": "3.2.25",
     "microbundle": "0.11.0",
-    "prettier": "1.18.2",
+    "prettier": "2.0.1",
     "rimraf": "2.6.3",
     "rxjs": "6.5.2"
   }