Upgrade eslint to v9 with flat config

eslint.config.mjs

@@ -0,0 +1,53 @@
+import js from "@eslint/js";
+import prettier from "eslint-config-prettier";
+import globals from "globals";
+import ts from "typescript-eslint";
+
+/** @type {import('eslint').Linter.Config[]} */
+export default [
+	js.configs.recommended,
+	...ts.configs.recommended,
+	prettier,
+	{
+		languageOptions: {
+			globals: {
+				...globals.browser,
+				...globals.jquery,
+				...globals.node,
+			},
+		},
+		rules: {
+			"no-unused-vars": "off",
+			"@typescript-eslint/no-unused-vars": "off",
+			"@typescript-eslint/no-explicit-any": "off",
+			"@typescript-eslint/no-this-alias": "off",
+			"@typescript-eslint/no-empty-object-type": "off",
+			"@typescript-eslint/triple-slash-reference": "off",
+		},
+	},
+	{
+		files: ["tests/**/*.js"],
+		languageOptions: {
+			globals: {
+				...globals.qunit,
+			},
+		},
+	},
+	{
+		ignores: [
+			".DS_Store",
+			"node_modules",
+			"build",
+			"dist",
+			"coverage",
+			".vercel",
+			"package",
+			".env",
+			".env.*",
+			"!.env.example",
+			"pnpm-lock.yaml",
+			"package-lock.json",
+			"yarn.lock",
+		],
+	},
+];

package.json

@@ -31,22 +31,23 @@
   },
   "license": "MIT",
   "devDependencies": {
+    "@eslint/js": "^9.9.0",
     "@rollup/plugin-commonjs": "^25.0.7",
     "@types/jquery": "^3.5.30",
-    "@typescript-eslint/eslint-plugin": "^7.10.0",
-    "@typescript-eslint/parser": "^7.10.0",
     "esbuild": "^0.21.4",
-    "eslint": "^8.56.0",
+    "eslint": "^9.9.0",
     "eslint-config-prettier": "^9.1.0",
     "glob": "^10.3.10",
+    "globals": "^15.9.0",
     "jquery": "^3.7.1",
     "prettier": "^3.2.5",
     "qunit": "^2.21.0",
     "rollup": "^4.17.2",
     "rollup-plugin-copy": "^3.5.0",
     "rollup-plugin-esbuild": "^6.1.1",
     "tslib": "^2.6.2",
-    "typescript": "^5.4.5"
+    "typescript": "^5.4.5",
+    "typescript-eslint": "^8.1.0"
   },
   "peerDependencies": {
     "jquery": ">=1.9.0"