Bump to eslint 9.8

Morph to eslint.config.mjs and fix unused warnings for caught exceptions.

eslint.config.mjs

@@ -0,0 +1,42 @@
+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 [
+    ...compat.extends('eslint:recommended'),
+    {
+        languageOptions: {
+            globals: {
+                ...globals.browser,
+            },
+
+            ecmaVersion: 'latest',
+            sourceType: 'module',
+        },
+
+        rules: {
+            'indent': ['error', 4],
+            'linebreak-style': ['error', 'unix'],
+            'quotes': ['error', 'single'],
+            'semi': ['error', 'always'],
+            'no-unused-vars': [
+                'error',
+                {
+                    argsIgnorePattern: '^_',
+                    caughtErrorsIgnorePattern: '^_',
+                    varsIgnorePattern: '^_',
+                },
+            ],
+        },
+    },
+];