Add no-shadow and no-unused-vars rules

- no shadow to allow reusing variable name for different function args
- no unused vars to help up speed up development when adding or removing as well as testing new things

client/package.json

@@ -40,6 +40,8 @@
       "../package.json"
     ],
     "rules": {
+      "no-unused-vars": "warn",
+      "no-shadow": "off",
       "import/no-extraneous-dependencies": [
         "error",
         {