replace deprecated .eslintrc with eslint.config.mjs

I tried to include all the rules and plugins from the old config as
far as they are compatible with eslint 9.

eslint-config-standard and eslint-config-standard-react seem to be
dead and have been forked into neoconfig.The promise and n plugin is
included in neoconfig afaik and doesn't need to be added explicitly.

eslint.config.mjs

@@ -0,0 +1,50 @@
+import globals from "globals";
+import hooksPlugin from "eslint-plugin-react-hooks";
+import importPlugin from "eslint-plugin-import";
+import jsxA11y from "eslint-plugin-jsx-a11y";
+import pluginJest from "eslint-plugin-jest";
+import pluginJs from "@eslint/js";
+import neostandard, { plugins } from "neostandard";
+
+export default [
+    ...neostandard(),
+    jsxA11y.flatConfigs.recommended,
+    importPlugin.flatConfigs.recommended,
+    {
+        files: ["**/*.{js,mjs,cjs,jsx,mjsx,ts,tsx,mtsx,jest.jsx,jest.js}"],
+        ignores: ["node_modules/", "venv/", "static/"],
+        languageOptions: {
+            ...jsxA11y.flatConfigs.recommended.languageOptions,
+            globals: {
+                ...globals.browser,
+                ...pluginJest.environments.globals.globals,
+                ...globals.jquery,
+            },
+            ecmaVersion: "latest",
+            parserOptions: {
+                ecmaFeatures: {
+                    jsx: true,
+                    "experimentalObjectRestSpread": true,
+                },
+            },
+        },
+        plugins: {
+            jest: pluginJest,
+            "react-hooks": hooksPlugin,
+        },
+        rules: {
+            "no-restricted-syntax": ["error", "TemplateLiteral"],
+            "jsx-a11y/no-onchange": "off",
+            "@stylistic/jsx-quotes": [2, "prefer-double"],
+            ...hooksPlugin.configs.recommended.rules,
+        },
+        settings: {
+            "import/core-modules": ["django"],
+            "import/resolver": {
+                node: {
+                    extensions: [".js", ".jsx"],
+                },
+            },
+        },
+    },
+];

package.json

@@ -36,32 +36,30 @@
     "@babel/plugin-transform-runtime": "7.25.9",
     "@babel/preset-env": "7.26.0",
     "@babel/preset-react": "7.25.9",
+    "@eslint/js": "9.13.0",
     "@maplibre/maplibre-gl-leaflet": "0.0.22",
     "@react-leaflet/core": "^2.1.0",
     "@testing-library/jest-dom": "6.4.8",
     "@testing-library/react": "15.0.7",
     "eslint": "9.15.0",
-    "eslint-config-standard": "17.1.0",
-    "eslint-config-standard-jsx": "11.0.0",
     "eslint-plugin-import": "2.31.0",
     "eslint-plugin-jest": "28.9.0",
     "eslint-plugin-jsx-a11y": "6.10.2",
-    "eslint-plugin-n": "17.14.0",
-    "eslint-plugin-promise": "7.2.1",
-    "eslint-plugin-react": "7.37.2",
     "eslint-plugin-react-hooks": "5.0.0",
     "esquery": "1.6.0",
+    "globals": "15.12.0",
     "husky": "9.0.11",
     "jest": "29.7.0",
     "jest-environment-jsdom": "29.7.0",
-    "lint-staged": "15.2.10"
+    "lint-staged": "15.2.10",
+    "neostandard": "0.11.7"
   },
   "repository": {
     "type": "git",
     "url": "git@github.com:liqd/adhocracy4.git"
   },
   "scripts": {
-    "lint": "eslint adhocracy4 --ext .js,.jsx",
+    "lint": "eslint adhocracy4",
     "lint-staged": "lint-staged",
     "lint-fix": "eslint --fix --ext .js,.jsx .",
     "prepare": "husky",