Upgrade to eslint v9 and get tests passing

Author: camertron

.eslintrc.js

@@ -0,0 +1,42 @@
+const eslintPlugin = require('eslint-plugin-eslint-plugin')
+const github = require('eslint-plugin-github')
+
+module.exports = [
+  github.getFlatConfigs().recommended,
+  eslintPlugin.configs['flat/recommended'],
+  {
+    languageOptions: {
+      parserOptions: {
+        ecmaVersion: 'latest',
+      },
+    },
+    env: {
+      commonjs: true,
+      node: true,
+    },
+    rules: {
+      'import/no-commonjs': 'off',
+      'no-shadow': 'off',
+      'no-unused-vars': [
+        'error',
+        {
+          varsIgnorePattern: '^_',
+        },
+      ],
+    },
+    overrides: [
+      {
+        files: ['**/*.test.js'],
+        env: {
+          jest: true,
+        },
+      },
+      {
+        files: ['.eslintrc.js'],
+        rules: {
+          'filenames/match-regex': 'off',
+        },
+      },
+    ],
+  }
+]