eslint - configure and setup auto linting

.eslintignore

@@ -0,0 +1,13 @@
+src/engine262
+src/tailwind.output.css
+
+# dependencies
+/node_modules
+/.pnp
+.pnp.js
+
+# testing
+/coverage
+
+# production
+/build

.eslintrc.json

@@ -0,0 +1,3 @@
+{
+  "extends": "react-app"
+}

package.json

@@ -31,7 +31,8 @@
     "start": "react-scripts start",
     "build": "react-scripts build",
     "test": "react-scripts test",
-    "eject": "react-scripts eject"
+    "eject": "react-scripts eject",
+    "lint": "eslint --ext js,jsx,ts,tsx src"
   },
   "eslintConfig": {
     "extends": "react-app"