chore: upgrade eslint to v9 (#54)

eslint.config.mjs

@@ -0,0 +1,31 @@
+import globals from "globals";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+import js from "@eslint/js";
+import { FlatCompat } from "@eslint/eslintrc";
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+const compat = new FlatCompat({
+    baseDirectory: __dirname,
+    recommendedConfig: js.configs.recommended,
+    allConfig: js.configs.all
+});
+
+export default [{
+    ignores: ["dist/*.js"],
+}, ...compat.extends("chartjs"), {
+    languageOptions: {
+        globals: {
+            ...globals.browser,
+            ...globals.node,
+        },
+
+        ecmaVersion: 2020,
+        sourceType: "module",
+    },
+
+    rules: {
+        complexity: [1, 15],
+    },
+}];