feat: ESLint Flat Config (v9 support #2229) (#2426)

* Flat config

* undo accidental formatting changes

* remove extra newline

eslint.config.mjs

@@ -0,0 +1,76 @@
+//@ts-check
+
+import eslint from '@eslint/js';
+import tseslint from 'typescript-eslint';
+import stylistic from "@stylistic/eslint-plugin-js"
+import * as importPlugin from "eslint-plugin-import"
+
+export default tseslint.config(
+  eslint.configs.recommended,
+  tseslint.configs.eslintRecommended,
+  ...tseslint.configs.recommendedTypeChecked,
+  { ignores: ["dist", "node_modules", "*.config.*js"] },
+  {
+    plugins: {
+      stylistic,
+      importPlugin
+    },
+    languageOptions: {
+      parser: tseslint.parser,
+      parserOptions: {
+        project: true,
+        sourceType: "module",
+        ecmaVersion: "latest"
+      }
+    },
+    rules: {
+      "stylistic/arrow-parens": ["error", "always"],
+      "stylistic/object-curly-spacing": ["error", "always"],
+      "@typescript-eslint/no-floating-promises": "off",
+      "@typescript-eslint/no-misused-promises": ["off", { checksVoidReturn: false }],
+      '@typescript-eslint/no-unused-vars': ['warn', { argsIgnorePattern: '^_' }],
+      "@typescript-eslint/no-non-null-assertion": "off",
+      "importPlugin/first": "error",
+      "importPlugin/newline-after-import": "off",
+      "importPlugin/no-default-export": "off",
+      "importPlugin/no-duplicates": "error",
+      "importPlugin/no-unresolved": ["error", { ignore: ['^virtual:', '\\?inline$', '\\?raw$', '\\?asset&asarUnpack'] }],
+      "importPlugin/order": ["error", {
+        'groups': ['builtin', 'external', ['internal', 'index', 'sibling'], 'parent', 'type'],
+        'newlines-between': 'always-and-inside-groups',
+        'alphabetize': { order: 'ignore', caseInsensitive: false }
+      }],
+      "importPlugin/prefer-default-export": "off",
+      "camelcase": ["error", { properties: "never" }],
+      "class-methods-use-this": "off",
+      "stylistic/lines-around-comment": ["error", {
+        beforeBlockComment: false,
+        afterBlockComment: false,
+        beforeLineComment: false,
+        afterLineComment: false,
+      }],
+      "stylistic/max-len": "off",
+      "stylistic/no-mixed-operators": "error",
+      "stylistic/no-multi-spaces": ["error", { ignoreEOLComments: true }],
+      "stylistic/no-tabs": "error",
+      "no-void": "error",
+      "no-empty": "off",
+      "prefer-promise-reject-errors": "off",
+      "stylistic/quotes": ["error", "single", {
+        avoidEscape: true,
+        allowTemplateLiterals: false,
+      }],
+      "stylistic/quote-props": ["error", "consistent"],
+      "stylistic/semi": ["error", "always"],
+    },
+    settings: {
+      'import/parsers': {
+        '@typescript-eslint/parser': ['.ts']
+      },
+      'import/resolver': {
+        typescript: {},
+        exports: {},
+      },
+    },
+  },
+);