Add lint-staged to only lint staged files

Currently, linting runs on every pre-commit for the whole project.
This can be slow for medium to large sized projects.
With lint-staged, linting runs only on git staged files.

Author: satazor

README.md

@@ -31,8 +31,11 @@ This is how a `package.json` could look like when making use of these scripts:
     "uphold-scripts": "^0.4.0"
   },
   "pre-commit": [
-    "lint"
-  ]
+    "lint-staged -q"
+  ],
+  "lint-staged": {
+    "*.{js,mjs,ts}": ["uphold-scripts lint"]
+  }
 }
 ```
 

package.json

@@ -19,6 +19,7 @@
     "eslint": "^7.32.0",
     "eslint-config-uphold": "^2.0.0",
     "jest": "^27.3.1",
+    "lint-staged": "^12.3.4",
     "pre-commit": "^1.2.2",
     "prettier": "^2.4.1"
   }