lint-staged should ignore package.json and package-lock.json

these are formatted by npm and would otherwise cause too much churn

.lintstagedrc.json

@@ -2,5 +2,5 @@
   "linters": {
     "(bin/*|*.{js,json}|**/*.{js,json})": ["prettier-eslint --write", "git add"]
   },
-  "ignore": ["docs/**/*.js", "test/**/*.fixture.js"]
+  "ignore": ["docs/**/*.js", "test/**/*.fixture.js", "package*.json"]
 }