Add ESLint

package.json

@@ -7,8 +7,11 @@
     "preact": "10.17.1"
   },
   "devDependencies": {
+    "@eslint/js": "^9.11.1",
     "@parcel/packager-raw-url": "^2.0.0",
     "@parcel/transformer-webmanifest": "^2.0.0",
+    "eslint": "^9.11.1",
+    "globals": "^15.9.0",
     "node-static": "^0.7.11",
     "parcel": "^2.0.0",
     "split": "^1.0.1",
@@ -16,7 +19,8 @@
   },
   "scripts": {
     "start": "node ./dev-server.js",
-    "build": "parcel build"
+    "build": "parcel build",
+    "lint": "eslint"
   },
   "private": true,
   "targets": {