chore: migrate to ESLint 9 (#2358)

* fix: formatting errors

* chore: migrate to ESLint 9

Author: rzhao271

.eslintrc.js

@@ -0,0 +1,63 @@
+const { FlatCompat } = require('@eslint/eslintrc');
+const tsParser = require('@typescript-eslint/parser');
+const tsPlugin = require('@typescript-eslint/eslint-plugin');
+const reactPlugin = require('eslint-plugin-react');
+const headersPlugin = require('eslint-plugin-headers');
+
+const compat = new FlatCompat({
+  baseDirectory: __dirname,
+});
+
+module.exports = [
+  {
+    ignores: ['**/*.d.ts', 'src/test/**/*.ts', 'demos/**/*', '**/*.js', 'testWorkspace/**'],
+  },
+  {
+    linterOptions: {
+      reportUnusedDisableDirectives: 'off',
+    },
+  },
+  ...compat.extends('plugin:react/recommended', 'plugin:@typescript-eslint/recommended'),
+  {
+    files: ['src/**/*.ts'],
+    languageOptions: {
+      parser: tsParser,
+      ecmaVersion: 2018,
+      sourceType: 'module',
+    },
+    plugins: {
+      '@typescript-eslint': tsPlugin,
+      react: reactPlugin,
+      headers: headersPlugin,
+    },
+    settings: {
+      react: {
+        pragma: 'h',
+        version: '16.3',
+      },
+    },
+    rules: {
+      // Temporary until CDP is moved out, which is where most violations are:
+      '@typescript-eslint/ban-types': 'off',
+
+      '@typescript-eslint/no-var-requires': 'off',
+      '@typescript-eslint/no-require-imports': 'off',
+      '@typescript-eslint/no-use-before-define': 'off',
+      '@typescript-eslint/explicit-function-return-type': 'off',
+      '@typescript-eslint/no-namespace': 'off',
+      '@typescript-eslint/no-empty-object-type': 'off',
+      '@typescript-eslint/no-explicit-any': 'off',
+      '@typescript-eslint/no-non-null-asserted-optional-chain': 'off',
+      '@typescript-eslint/no-unsafe-function-type': 'off',
+      '@typescript-eslint/no-unused-expressions': 'off',
+      '@typescript-eslint/ban-ts-comment': 'off',
+      'prefer-const': ['error', { destructuring: 'all' }],
+      '@typescript-eslint/explicit-module-boundary-types': 'off',
+      // Current repository headers use a legacy style that would require mass edits to older files.
+      'headers/header-format': 'off',
+      'react/no-unescaped-entities': 'off',
+      'react/prop-types': 'off',
+      '@typescript-eslint/no-unused-vars': 'off',
+    },
+  },
+];