use explicit path for prettierrc file, closes #289

gpx/package.json

@@ -25,7 +25,7 @@
     "scripts": {
         "build": "tsc",
         "postinstall": "npm run build",
-        "lint": "prettier --check . && eslint .",
-        "format": "prettier --write ."
+        "lint": "prettier --check . --config ../.prettierrc && eslint .",
+        "format": "prettier --write . --config ../.prettierrc"
     }
 }